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Queryable::SelectMany<TSource, TResult> Method (IQueryable<TSource>, Expression<Func<TSource, Int32, IEnumerable<TResult>>>)

Projects each element of a sequence to an IEnumerable<T> and combines the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)
[ExtensionAttribute]
public:
generic<typename TSource, typename TResult>
static IQueryable<TResult>^ SelectMany(
	IQueryable<TSource>^ source, 
	Expression<Func<TSource, int, IEnumerable<TResult>^>^>^ selector
)

Type Parameters

TSource

The type of the elements of source.

TResult

The type of the elements of the sequence returned by the function represented by selector.

Parameters

source
Type: System.Linq::IQueryable<TSource>

A sequence of values to project.

selector
Type: System.Linq.Expressions::Expression<Func<TSource, Int32, IEnumerable<TResult>>>

A projection function to apply to each element; the second parameter of this function represents the index of the source element.

Return Value

Type: System.Linq::IQueryable<TResult>
An IQueryable<T> whose elements are the result of invoking a one-to-many projection function on each element of the input 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 nullptr.

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 SelectMany<TSource, TResult>(IQueryable<TSource>, Expression<Func<TSource, Int32, IEnumerable<TResult>>>) method generates a MethodCallExpression that represents calling SelectMany<TSource, TResult>(IQueryable<TSource>, Expression<Func<TSource, Int32, IEnumerable<TResult>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(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 SelectMany<TSource, TResult>(IQueryable<TSource>, Expression<Func<TSource, Int32, IEnumerable<TResult>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it invokes selector on each element of source to project it into an enumerable form. Each enumerable result incorporates the index of the source element. It then concatenates the enumerable results into a single, one-dimensional sequence.

The following code example demonstrates how to use SelectMany<TSource, TResult>(IQueryable<TSource>, Expression<Func<TSource, Int32, IEnumerable<TResult>>>) to perform a one-to-many projection over an array and use the index of each source element.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.5.1, 4.5, 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

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

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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