Queryable::Select<TSource, TResult> Method (IQueryable<TSource>^, Expression<Func<TSource, Int32, TResult>^>^)
Projects each element of a sequence into a new form by incorporating the element's index.
Assembly: System.Core (in System.Core.dll)
public: generic<typename TSource, typename TResult> [ExtensionAttribute] static IQueryable<TResult>^ Select( IQueryable<TSource>^ source, Expression<Func<TSource, int, TResult>^>^ selector )
Parameters
- source
-
Type:
System.Linq::IQueryable<TSource>^
A sequence of values to project.
- selector
-
Type:
System.Linq.Expressions::Expression<Func<TSource, Int32, TResult>^>^
A projection function to apply to each element.
Return Value
Type: System.Linq::IQueryable<TResult>^An IQueryable<T> whose elements are the result of invoking a projection function on each element of source.
Type Parameters
- TSource
The type of the elements of source.
- TResult
The type of the value returned by the function represented by selector.
| Exception | Condition |
|---|---|
| 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 Select<TSource, TResult>(IQueryable<TSource>^, Expression<Func<TSource, Int32, TResult>^>^) method generates a MethodCallExpression that represents calling Select<TSource, TResult>(IQueryable<TSource>^, Expression<Func<TSource, Int32, 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 Select<TSource, TResult>(IQueryable<TSource>^, Expression<Func<TSource, Int32, TResult>^>^) depend 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 a different form.
The following code example demonstrates how to use Select<TSource, TResult>(IQueryable<TSource>^, Expression<Func<TSource, Int32, TResult>^>^) to project over a sequence of values and use the index of each element in the projected form.
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1