# Queryable.Average 方法

## 多載

 Average(IQueryable) 計算 Single 值序列的平均值。Computes the average of a sequence of Single values. Average(IQueryable>) 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>) 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>) 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>) 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) 計算 Int64 值序列的平均值。Computes the average of a sequence of Int64 values. Average(IQueryable) 計算 Int32 值序列的平均值。Computes the average of a sequence of Int32 values. Average(IQueryable) 計算 Double 值序列的平均值。Computes the average of a sequence of Double values. Average(IQueryable) 計算 Decimal 值序列的平均值。Computes the average of a sequence of Decimal values. Average(IQueryable>) 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(IQueryable, Expression>) 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(IQueryable, Expression>>) 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(IQueryable, Expression>>) 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(IQueryable, Expression>>) 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(IQueryable, Expression>>) 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(IQueryable, Expression>) 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(IQueryable, Expression>) 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(IQueryable, Expression>) 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(IQueryable, Expression>) 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(IQueryable, Expression>>) 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>)

``````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>

Single

#### 例外狀況

`source``null``source` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Nullable<Single>>)

``````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>>

Nullable<Single>

#### 例外狀況

`source``null``source` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Nullable<Int64>>)

``````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>>

Nullable<Double>

#### 例外狀況

`source``null``source` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Nullable<Double>>)

``````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>>

Nullable<Double>

#### 例外狀況

`source``null``source` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Nullable<Int32>>)

``````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>>

Nullable<Double>

#### 例外狀況

`source``null``source` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Int64>)

``````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>

Double

#### 例外狀況

`source``null``source` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Int32>)

``````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>

Double

#### 例外狀況

`source``null``source` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Double>)

``````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>

Double

#### 例外狀況

`source``null``source` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Decimal>)

``````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>

Decimal

#### 例外狀況

`source``null``source` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

## Average(IQueryable<Nullable<Decimal>>)

``````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>>

#### 傳回

Nullable<Decimal>

#### 例外狀況

`source``null``source` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

selector
Expression<Func<TSource,Single>>

Single

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

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

Nullable<Single>

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the `source` parameter.

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

``````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>

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

Nullable<Double>

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

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

Nullable<Double>

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the `source` parameter.

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

``````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>

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

Nullable<Double>

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

selector
Expression<Func<TSource,Int64>>

Double

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

selector
Expression<Func<TSource,Int32>>

Double

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

selector
Expression<Func<TSource,Double>>

Double

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

selector
Expression<Func<TSource,Decimal>>

Decimal

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

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

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.

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

``````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>

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

#### 傳回

Nullable<Decimal>

#### 例外狀況

`source``selector``null``source` or `selector` is `null`.

### 範例

``````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

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 `source`It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the `source` parameter.