MoreEnumerable.TagFirstLast(TSource, TResult) Method

Returns a sequence resulting from applying a function to each element in the source sequence with additional parameters indicating whether the element is the first and/or last of the sequence.

Namespace: MoreLinq
Assembly: MoreLinq (in MoreLinq.dll) Version: 2.1.0

Syntax

C++

Copy

public static IEnumerable<TResult> TagFirstLast<TSource, TResult>(
	this IEnumerable<TSource> source,
	Func<TSource, bool, bool, TResult> resultSelector
)

<ExtensionAttribute>
Public Shared Function TagFirstLast(Of TSource, TResult) ( 
	source As IEnumerable(Of TSource),
	resultSelector As Func(Of TSource, Boolean, Boolean, TResult)
) As IEnumerable(Of TResult)

public:
[ExtensionAttribute]
generic<typename TSource, typename TResult>
static IEnumerable<TResult>^ TagFirstLast(
	IEnumerable<TSource>^ source, 
	Func<TSource, bool, bool, TResult>^ resultSelector
)

[<ExtensionAttribute>]
static member TagFirstLast : 
        source : IEnumerable<'TSource> * 
        resultSelector : Func<'TSource, bool, bool, 'TResult> -> IEnumerable<'TResult>

Parameters

source: Type: System.Collections.GenericIEnumerableTSource
The source sequence.
resultSelector: Type: SystemFuncTSource, Boolean, Boolean, TResult
A function that determines how to project the each element along with its first or last tag.

Type Parameters

TSource: The type of the elements of source.
TResult: The type of the element of the returned sequence.

Return Value

Type: IEnumerableTResult
Returns the resulting sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerableTSource. 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).

Remarks

This operator uses deferred execution and streams its results.

Examples

Copy

var numbers = new[] { 123, 456, 789 };
var result = numbers.TagFirstLast((num, fst, lst) => new 
             { 
                 Number = num,
                 IsFirst = fst, IsLast = lst
             });

The result variable, when iterated over, will yield { Number = 123, IsFirst = True, IsLast = False }, { Number = 456, IsFirst = False, IsLast = False } and { Number = 789, IsFirst = False, IsLast = True } in turn.

Reference

MoreEnumerable Class

MoreLinq Namespace