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Queryable.Max<TSource, TResult> Method (IQueryable<TSource>, Expression<Func<TSource, TResult>>)

Invokes a projection function on each element of a generic IQueryable<T> and returns the maximum resulting value.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

public static TResult Max<TSource, TResult>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, TResult>> selector
)

Type Parameters

TSource

The type of the elements of source.

TResult

The type of the value returned by the function represented by selector.

Parameters

source
Type: System.Linq.IQueryable<TSource>

A sequence of values to determine the maximum of.

selector
Type: System.Linq.Expressions.Expression<Func<TSource, TResult>>

A projection function to apply to each element.

Return Value

Type: TResult
The maximum value in the sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

source or selector is null.

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T, TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

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

The 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. The expected behavior is that it invokes selector on each element in source and returns the maximum value.

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.
*/

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5

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