Queryable.Average 方法

定義

計算數值序列的平均值。Computes the average of a sequence of numeric values.

多載

Average(IQueryable<Single>)

計算 Single 值序列的平均值。Computes the average of a sequence of Single values.

Average(IQueryable<Nullable<Single>>)

計算可為 Null 之 Single 值序列的平均值。Computes the average of a sequence of nullable Single values.

Average(IQueryable<Nullable<Int64>>)

計算可為 Null 之 Int64 值序列的平均值。Computes the average of a sequence of nullable Int64 values.

Average(IQueryable<Nullable<Double>>)

計算可為 Null 之 Double 值序列的平均值。Computes the average of a sequence of nullable Double values.

Average(IQueryable<Nullable<Int32>>)

計算可為 Null 之 Int32 值序列的平均值。Computes the average of a sequence of nullable Int32 values.

Average(IQueryable<Int64>)

計算 Int64 值序列的平均值。Computes the average of a sequence of Int64 values.

Average(IQueryable<Int32>)

計算 Int32 值序列的平均值。Computes the average of a sequence of Int32 values.

Average(IQueryable<Double>)

計算 Double 值序列的平均值。Computes the average of a sequence of Double values.

Average(IQueryable<Decimal>)

計算 Decimal 值序列的平均值。Computes the average of a sequence of Decimal values.

Average(IQueryable<Nullable<Decimal>>)

計算可為 Null 之 Decimal 值序列的平均值。Computes the average of a sequence of nullable Decimal values.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Single 值序列的平均值。Computes the average of a sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Single 值序列的平均值。Computes the average of a sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Int64 值序列的平均值。Computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Int32 值序列的平均值。Computes the average of a sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Double 值序列的平均值。Computes the average of a sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Int64 值序列的平均值。Computes the average of a sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Int32 值序列的平均值。Computes the average of a sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Double 值序列的平均值。Computes the average of a sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Decimal 值序列的平均值。Computes the average of a sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Decimal 值序列的平均值。Computes the average of a sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

Average(IQueryable<Single>)

計算 Single 值序列的平均值。Computes the average of a sequence of Single values.

public:
[System::Runtime::CompilerServices::Extension]
 static float Average(System::Linq::IQueryable<float> ^ source);
public static float Average (this System.Linq.IQueryable<float> source);
static member Average : System.Linq.IQueryable<single> -> single
<Extension()>
Public Function Average (source As IQueryable(Of Single)) As Single

參數

source
IQueryable<Single>

要計算平均值的 Single 值序列。A sequence of Single values to calculate the average of.

傳回

Single

值序列的平均。The average of the sequence of values.

例外狀況

sourcenullsource is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Int32>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.
Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

備註

Average(IQueryable<Single>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Single>)The Average(IQueryable<Single>) method generates a MethodCallExpression that represents calling Average(IQueryable<Single>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Single>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Single>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Nullable<Single>>)

計算可為 Null 之 Single 值序列的平均值。Computes the average of a sequence of nullable Single values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<float> Average(System::Linq::IQueryable<Nullable<float>> ^ source);
public static float? Average (this System.Linq.IQueryable<float?> source);
static member Average : System.Linq.IQueryable<Nullable<single>> -> Nullable<single>
<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Single))) As Nullable(Of Single)

參數

source
IQueryable<Nullable<Single>>

要計算其平均值的可為 Null 之 Single 值的序列。A sequence of nullable Single values to calculate the average of.

傳回

Nullable<Single>

值序列的平均值,或者,如果來源序列是空的或只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourcenullsource is null.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Nullable<Int64>>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

備註

Average(IQueryable<Nullable<Single>>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Nullable<Single>>)The Average(IQueryable<Nullable<Single>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Single>>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Nullable<Single>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Single>>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Nullable<Int64>>)

計算可為 Null 之 Int64 值序列的平均值。Computes the average of a sequence of nullable Int64 values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<long>> ^ source);
public static double? Average (this System.Linq.IQueryable<long?> source);
static member Average : System.Linq.IQueryable<Nullable<int64>> -> Nullable<double>
<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Long))) As Nullable(Of Double)

參數

source
IQueryable<Nullable<Int64>>

要計算其平均值的可為 Null 之 Int64 值的序列。A sequence of nullable Int64 values to calculate the average of.

傳回

Nullable<Double>

值序列的平均值,或者,如果來源序列是空的或只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourcenullsource is null.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Nullable<Int64>>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

備註

Average(IQueryable<Nullable<Int64>>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Nullable<Int64>>)The Average(IQueryable<Nullable<Int64>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Int64>>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Nullable<Int64>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Int64>>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Nullable<Double>>)

計算可為 Null 之 Double 值序列的平均值。Computes the average of a sequence of nullable Double values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<double>> ^ source);
public static double? Average (this System.Linq.IQueryable<double?> source);
static member Average : System.Linq.IQueryable<Nullable<double>> -> Nullable<double>
<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Double))) As Nullable(Of Double)

參數

source
IQueryable<Nullable<Double>>

要計算其平均值的可為 Null 之 Double 值的序列。A sequence of nullable Double values to calculate the average of.

傳回

Nullable<Double>

值序列的平均值,或者,如果來源序列是空的或只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourcenullsource is null.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Nullable<Int64>>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

備註

Average(IQueryable<Nullable<Double>>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Nullable<Double>>)The Average(IQueryable<Nullable<Double>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Double>>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Nullable<Double>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Double>>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Nullable<Int32>>)

計算可為 Null 之 Int32 值序列的平均值。Computes the average of a sequence of nullable Int32 values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<int>> ^ source);
public static double? Average (this System.Linq.IQueryable<int?> source);
static member Average : System.Linq.IQueryable<Nullable<int>> -> Nullable<double>
<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Integer))) As Nullable(Of Double)

參數

source
IQueryable<Nullable<Int32>>

要計算其平均值的可為 Null 之 Int32 值的序列。A sequence of nullable Int32 values to calculate the average of.

傳回

Nullable<Double>

值序列的平均值,或者,如果來源序列是空的或只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourcenullsource is null.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Nullable<Int64>>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

備註

Average(IQueryable<Nullable<Int32>>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Nullable<Int32>>)The Average(IQueryable<Nullable<Int32>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Int32>>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Nullable<Int32>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Int32>>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Int64>)

計算 Int64 值序列的平均值。Computes the average of a sequence of Int64 values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<long> ^ source);
public static double Average (this System.Linq.IQueryable<long> source);
static member Average : System.Linq.IQueryable<int64> -> double
<Extension()>
Public Function Average (source As IQueryable(Of Long)) As Double

參數

source
IQueryable<Int64>

要計算平均值的 Int64 值序列。A sequence of Int64 values to calculate the average of.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourcenullsource is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Int32>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.
Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

備註

Average(IQueryable<Int64>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Int64>)The Average(IQueryable<Int64>) method generates a MethodCallExpression that represents calling Average(IQueryable<Int64>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Int64>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Int64>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Int32>)

計算 Int32 值序列的平均值。Computes the average of a sequence of Int32 values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<int> ^ source);
public static double Average (this System.Linq.IQueryable<int> source);
static member Average : System.Linq.IQueryable<int> -> double
<Extension()>
Public Function Average (source As IQueryable(Of Integer)) As Double

參數

source
IQueryable<Int32>

要計算平均值的 Int32 值序列。A sequence of Int32 values to calculate the average of.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourcenullsource is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Int32>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.
Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

備註

Average(IQueryable<Int32>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Int32>)The Average(IQueryable<Int32>) method generates a MethodCallExpression that represents calling Average(IQueryable<Int32>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Int32>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Int32>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Double>)

計算 Double 值序列的平均值。Computes the average of a sequence of Double values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<double> ^ source);
public static double Average (this System.Linq.IQueryable<double> source);
static member Average : System.Linq.IQueryable<double> -> double
<Extension()>
Public Function Average (source As IQueryable(Of Double)) As Double

參數

source
IQueryable<Double>

要計算平均值的 Double 值序列。A sequence of Double values to calculate the average of.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourcenullsource is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Int32>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.
Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

備註

Average(IQueryable<Double>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Double>)The Average(IQueryable<Double>) method generates a MethodCallExpression that represents calling Average(IQueryable<Double>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Double>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Double>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Decimal>)

計算 Decimal 值序列的平均值。Computes the average of a sequence of Decimal values.

public:
[System::Runtime::CompilerServices::Extension]
 static System::Decimal Average(System::Linq::IQueryable<System::Decimal> ^ source);
public static decimal Average (this System.Linq.IQueryable<decimal> source);
static member Average : System.Linq.IQueryable<decimal> -> decimal
<Extension()>
Public Function Average (source As IQueryable(Of Decimal)) As Decimal

參數

source
IQueryable<Decimal>

要計算平均值的 Decimal 值序列。A sequence of Decimal values to calculate the average of.

傳回

Decimal

值序列的平均。The average of the sequence of values.

例外狀況

sourcenullsource is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Int32>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.
Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

備註

Average(IQueryable<Decimal>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Decimal>)The Average(IQueryable<Decimal>) method generates a MethodCallExpression that represents calling Average(IQueryable<Decimal>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Decimal>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Decimal>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average(IQueryable<Nullable<Decimal>>)

計算可為 Null 之 Decimal 值序列的平均值。Computes the average of a sequence of nullable Decimal values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<System::Decimal> Average(System::Linq::IQueryable<Nullable<System::Decimal>> ^ source);
public static decimal? Average (this System.Linq.IQueryable<decimal?> source);
static member Average : System.Linq.IQueryable<Nullable<decimal>> -> Nullable<decimal>
<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Decimal))) As Nullable(Of Decimal)

參數

source
IQueryable<Nullable<Decimal>>

要計算其平均值的可為 Null 之 Decimal 值的序列。A sequence of nullable Decimal values to calculate the average of.

傳回

Nullable<Decimal>

值序列的平均值,或者,如果來源序列是空的或只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourcenullsource is null.

範例

下列程式碼範例示範如何使用 Average(IQueryable<Nullable<Int64>>) 來計算值序列的平均值。The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要擴充範例以符合本主題內容,請以具有適當數值類型的項目取代來源序列的項目。To extend the example to this topic, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.
Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

備註

Average(IQueryable<Nullable<Decimal>>)方法 MethodCallExpression 會產生表示呼叫本身的 Average(IQueryable<Nullable<Decimal>>)The Average(IQueryable<Nullable<Decimal>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Decimal>>) itself. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average(IQueryable<Nullable<Decimal>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Decimal>>) depends on the implementation of the type of the source parameter. 預期的行為是它會計算中值的平均值 sourceThe expected behavior is that it calculates the average of the values in source.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Single 值序列的平均值。Computes the average of a sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static float Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, float> ^> ^ selector);
public static float Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,float>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, single>> -> single
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Single))) As Single

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Single>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Single

值序列的平均。The average of the sequence of values.

例外狀況

sourceselectornullsource or selector is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Single 值序列的平均值。Computes the average of a sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<float> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<float>> ^> ^ selector);
public static float? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,float?>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<single>>> -> Nullable<single>
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Single)))) As Nullable(Of Single)

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Nullable<Single>>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Nullable<Single>

值序列的平均值;如果 source 序列是空的或是只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourceselectornullsource or selector is null.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 至參數所代表之的 Execute<TResult>(Expression) 方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Int64 值序列的平均值。Computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<long>> ^> ^ selector);
public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,long?>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<int64>>> -> Nullable<double>
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Long)))) As Nullable(Of Double)

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Nullable<Int64>>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Nullable<Double>

值序列的平均值;如果 source 序列是空的或是只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourceselectornullsource or selector is null.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Int32 值序列的平均值。Computes the average of a sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<int>> ^> ^ selector);
public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,int?>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<int>>> -> Nullable<double>
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Integer)))) As Nullable(Of Double)

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Nullable<Int32>>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Nullable<Double>

值序列的平均值;如果 source 序列是空的或是只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourceselectornullsource or selector is null.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 至參數所代表之的 Execute<TResult>(Expression) 方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Double 值序列的平均值。Computes the average of a sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<double>> ^> ^ selector);
public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,double?>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<double>>> -> Nullable<double>
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Double)))) As Nullable(Of Double)

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Nullable<Double>>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Nullable<Double>

值序列的平均值;如果 source 序列是空的或是只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourceselectornullsource or selector is null.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Int64 值序列的平均值。Computes the average of a sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, long> ^> ^ selector);
public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,long>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, int64>> -> double
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Long))) As Double

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Int64>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourceselectornullsource or selector is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Int32 值序列的平均值。Computes the average of a sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, int> ^> ^ selector);
public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,int>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, int>> -> double
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Integer))) As Double

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Int32>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourceselectornullsource or selector is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Double 值序列的平均值。Computes the average of a sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, double> ^> ^ selector);
public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,double>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, double>> -> double
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Double))) As Double

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Double>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Double

值序列的平均。The average of the sequence of values.

例外狀況

sourceselectornullsource or selector is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>)

計算在輸入序列中各項目上叫用投影函式後所取得之 Decimal 值序列的平均值。Computes the average of a sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Decimal Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, System::Decimal> ^> ^ selector);
public static decimal Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,decimal>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, decimal>> -> decimal
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Decimal))) As Decimal

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

用來計算平均值的值序列。A sequence of values that are used to calculate an average.

selector
Expression<Func<TSource,Decimal>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Decimal

值序列的平均。The average of the sequence of values.

例外狀況

sourceselectornullsource or selector is null.

source 沒有包含任何項目。source contains no elements.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>)

計算在輸入序列中各項目上叫用投影函式後所取得可為 Null 之 Decimal 值序列的平均值。Computes the average of a sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<System::Decimal> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<System::Decimal>> ^> ^ selector);
public static decimal? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,decimal?>> selector);
static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<decimal>>> -> Nullable<decimal>
<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Decimal)))) As Nullable(Of Decimal)

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IQueryable<TSource>

要計算平均值的值序列。A sequence of values to calculate the average of.

selector
Expression<Func<TSource,Nullable<Decimal>>>

要套用到每個項目的投影函式。A projection function to apply to each element.

傳回

Nullable<Decimal>

值序列的平均值;如果 source 序列是空的或是只包含 null 值,則為 nullThe average of the sequence of values, or null if the source sequence is empty or contains only null values.

例外狀況

sourceselectornullsource or selector is null.

範例

下列程式碼範例示範如何使用 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) 來計算 String 類型值序列中的平均長度 StringThe following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

注意

這個程式碼範例會使用此多載方法的多載,這個多載不是本主題描述的特定多載。This code example uses an overload of this overloaded method that is different from the specific overload that this topic describes. 若要將此範例延伸到本主題中使用,請變更 selector 函式的主體。To extend the example to this topic, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.
Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

備註

這個方法至少有一個類型的參數 Expression<TDelegate> ,其型別引數是其中一種 Func<T,TResult> 類型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 針對這些參數,您可以傳入 lambda 運算式,並將其編譯為 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>)方法 MethodCallExpression 會產生,代表呼叫 Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) 本身做為已建立的泛型方法。The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) itself as a constructed generic method. 然後,它會將傳遞 MethodCallExpression 給以 Execute<TResult>(Expression) 參數的屬性所表示的方法 IQueryProvider Provider sourceIt then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

執行表示呼叫的運算式樹狀架構所產生的查詢行為, Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) 取決於參數類型的實作為 sourceThe query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) depends on the implementation of the type of the source parameter. 預期的行為是在叫用 source 每個值之後,計算值的平均值 selectorThe expected behavior is that it calculates the average of the values in source after invoking selector on each value.

適用於