Queryable.ElementAtOrDefault<TSource> Method

Returns the element at a specified index in a sequence or a default value if the index is out of range.

Namespace:  System.Linq
Assemblies:   System.Linq.Queryable (in System.Linq.Queryable.dll)
  System.Core (in System.Core.dll)

public static TSource ElementAtOrDefault<TSource>(
	this IQueryable<TSource> source,
	int index
)

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return an element from.

index
Type: System.Int32

The zero-based index of the element to retrieve.

Return Value

Type: TSource
default(TSource) if index is outside the bounds of source; otherwise, the element at the specified position in source.

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 is null.

The ElementAtOrDefault<TSource>(IQueryable<TSource>, Int32) method generates a MethodCallExpression that represents calling ElementAtOrDefault<TSource>(IQueryable<TSource>, Int32) 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 ElementAtOrDefault<TSource>(IQueryable<TSource>, Int32) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the item at position index in source, or default(TSource) if index is outside the bounds of source.

The following code example demonstrates how to use ElementAtOrDefault<TSource>(IQueryable<TSource>, Int32). This example uses a value for index that is outside the bounds of the source sequence.

            string[] names = { "Hartono, Tommy", "Adams, Terry",
                               "Andersen, Henriette Thaulow",
                               "Hedlund, Magnus", "Ito, Shu" };

            int index = 20;

            string name = names.AsQueryable().ElementAtOrDefault(index);

            Console.WriteLine(
                "The name chosen at index {0} is '{1}'.",
                index,
                String.IsNullOrEmpty(name) ? "[NONE AT THIS INDEX]" : name);

            /*
                This code produces the following output:

                The name chosen at index 20 is '[NONE AT THIS INDEX]'.
            */

.NET Framework

Supported in: 4.6, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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