Queryable.Max 方法

定義

多載

Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>)

對泛型 IQueryable<T> 的每個項目叫用投影函式,並傳回最大的結果值。Invokes a projection function on each element of a generic IQueryable<T> and returns the maximum resulting value.

Max<TSource>(IQueryable<TSource>)

傳回泛型 IQueryable<T> 中的最大值。Returns the maximum value in a generic IQueryable<T>.

Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>)

對泛型 IQueryable<T> 的每個項目叫用投影函式,並傳回最大的結果值。Invokes a projection function on each element of a generic IQueryable<T> and returns the maximum resulting value.

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

類型參數

TSource

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

TResult

selector 表示之函式所傳回值的型別。The type of the value returned by the function represented by selector.

參數

source
IQueryable<TSource>

要判斷最大值的值序列。A sequence of values to determine the maximum of.

selector
Expression<Func<TSource,TResult>>

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

傳回

TResult

序列中的最大值。The maximum value in the sequence.

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 Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) 來決定一連串投射值的最大值。The following code example demonstrates how to use Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) to determine the maximum value in a sequence of projected values.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void MaxEx2()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    // Add Pet.Age to the length of Pet.Name
    // to determine the "maximum" Pet object in the array.
    int max =
        pets.AsQueryable().Max(pet => pet.Age + pet.Name.Length);

    Console.WriteLine(
        "The maximum pet age plus name length is {0}.",
        max);
}

/*
    This code produces the following output:

    The maximum pet age plus name length is 14.
*/

Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Shared Sub MaxEx2()
    Dim pets() As Pet = {New Pet With {.Name = "Barley", .Age = 8}, _
                   New Pet With {.Name = "Boots", .Age = 4}, _
                   New Pet With {.Name = "Whiskers", .Age = 1}}

    ' Add Pet.Age to the length of Pet.Name
    ' to determine the "maximum" Pet object in the array.
    Dim max As Integer = _
        pets.AsQueryable().Max(Function(pet) pet.Age + pet.Name.Length)

    MsgBox(String.Format("The maximum pet age plus name length is {0}.", max))

    'This code produces the following output:

    'The maximum pet age plus name length is 14.

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>.

Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>)方法 MethodCallExpression 會產生,代表呼叫 Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) 本身做為已建立的泛型方法。The Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) method generates a MethodCallExpression that represents calling Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) 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, Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) 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 Max<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) depends on the implementation of the type of the source parameter. 預期的行為是它會 selector 在中的每個元素上叫用 source ,並傳回最大值。The expected behavior is that it invokes selector on each element in source and returns the maximum value.

適用於

Max<TSource>(IQueryable<TSource>)

傳回泛型 IQueryable<T> 中的最大值。Returns the maximum value in a generic IQueryable<T>.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource Max(System::Linq::IQueryable<TSource> ^ source);
public static TSource Max<TSource> (this System.Linq.IQueryable<TSource> source);
public static TSource? Max<TSource> (this System.Linq.IQueryable<TSource> source);
static member Max : System.Linq.IQueryable<'Source> -> 'Source
<Extension()>
Public Function Max(Of TSource) (source As IQueryable(Of TSource)) As TSource

類型參數

TSource

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

參數

source
IQueryable<TSource>

要判斷最大值的值序列。A sequence of values to determine the maximum of.

傳回

TSource

序列中的最大值。The maximum value in the sequence.

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 Max<TSource>(IQueryable<TSource>) 來判斷序列中的最大值。The following code example demonstrates how to use Max<TSource>(IQueryable<TSource>) to determine the maximum value in a sequence.

List<long> longs = new List<long> { 4294967296L, 466855135L, 81125L };

long max = longs.AsQueryable().Max();

Console.WriteLine("The largest number is {0}.", max);

/*
    This code produces the following output:

    The largest number is 4294967296.
*/
Dim longs As New List(Of Long)(New Long() {4294967296L, 466855135L, 81125L})

Dim max As Long = longs.AsQueryable().Max()

MsgBox(String.Format("The largest number is {0}.", max))

'This code produces the following output:

'The largest number is 4294967296.

備註

Max<TSource>(IQueryable<TSource>)方法 MethodCallExpression 會產生,代表呼叫 Max<TSource>(IQueryable<TSource>) 本身做為已建立的泛型方法。The Max<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Max<TSource>(IQueryable<TSource>) 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, Max<TSource>(IQueryable<TSource>) 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 Max<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. 預期的行為是它會在中傳回最大值 sourceThe expected behavior is that it returns the maximum value in source.

適用於