Enumerable.Where<TSource> Method (IEnumerable<TSource>, Func<TSource, Int32, Boolean>)
Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, int, bool> predicate )
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to filter.
- predicate
- Type: System.Func<TSource, Int32, Boolean>
A function to test each source element for a condition; the second parameter of the function represents the index of the source element.
Return Value
Type: System.Collections.Generic.IEnumerable<TSource>An IEnumerable<T> that contains elements from the input sequence that satisfy the condition.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
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 first argument of predicate represents the element to test. The second argument represents the zero-based index of the element within source.
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