Enumerable.First<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)
Returns the first element in a sequence that satisfies a specified condition.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
public static TSource First<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate )
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to return an element from.
- predicate
- Type: System.Func<TSource, Boolean>
A function to test each element for a condition.
Return Value
Type: TSourceThe first element in the sequence that passes the test in the specified predicate function.
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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
| InvalidOperationException | No element satisfies the condition in predicate. -or- The source sequence is empty. |
The First<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) method throws an exception if no matching element is found in source. To instead return a default value when no matching element is found, use the FirstOrDefault method.
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.
