Enumerable::SelectMany<TSource, TCollection, TResult> Method (IEnumerable<TSource>, Func<TSource, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>)
Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.
Assembly: System.Core (in System.Core.dll)
[ExtensionAttribute] public: generic<typename TSource, typename TCollection, typename TResult> static IEnumerable<TResult>^ SelectMany( IEnumerable<TSource>^ source, Func<TSource, IEnumerable<TCollection>^>^ collectionSelector, Func<TSource, TCollection, TResult>^ resultSelector )
The type of the elements of source.
The type of the intermediate elements collected by collectionSelector.
The type of the elements of the resulting sequence.
- Type: System.Collections.Generic::IEnumerable<>
A sequence of values to project.
- Type: System::Func<, IEnumerable<>>
A transform function to apply to each element of the input sequence.
- Type: System::Func<, , >
A transform function to apply to each element of the intermediate sequence.
Return ValueType: System.Collections.Generic::IEnumerable<>
An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function collectionSelector on each element of source and then mapping each of those sequence elements and their corresponding source element to a result element.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<>. 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).
source or collectionSelector or resultSelector is nullptr.
This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.
The method is useful when you have to keep the elements of source in scope for query logic that occurs after the call to . See the Example section for a code example. If there is a bidirectional relationship between objects of type TSource and objects of type TCollection, that is, if an object of type TCollection provides a property to retrieve the TSource object that produced it, you do not need this overload of . Instead, you can use SelectMany<TSource, TResult>(IEnumerable<TSource>, Func<TSource, IEnumerable<TResult>>) and navigate back to the TSource object through the TCollection object.
In query expression syntax, each from clause (Visual C#) or From clause (Visual Basic) after the initial one translates to an invocation of SelectMany.
The following code example demonstrates how to use to perform a one-to-many projection over an array and use a result selector function to keep each corresponding element from the source sequence in scope for the final call to Select.
.NET FrameworkSupported in: 4.6, 4.5, 4, 3.5
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
XNA FrameworkSupported in: 3.0
Portable Class LibrarySupported in: Portable Class Library
Supported in: Windows Phone 8.1
Supported in: Windows Phone Silverlight 8.1
Supported in: Windows Phone Silverlight 8