Queryable.First<'TSource> Method (IQueryable<'TSource>)
Returns the first element of a sequence.
Assembly: System.Core (in System.Core.dll)
Parameters
- source
-
Type:
System.Linq.IQueryable<'TSource>
The IQueryable<'T> to return the first element of.
Return Value
Type: TSourceThe first element in source.
Type Parameters
- TSource
The type of the elements of source.
| Exception | Condition |
|---|---|
| ArgumentNullException | source is null. |
| InvalidOperationException | The source sequence is empty. |
The First<'TSource>(IQueryable<'TSource>) method generates a MethodCallExpression that represents calling First<'TSource>(IQueryable<'TSource>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<'TResult>(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 First<'TSource>(IQueryable<'TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the first element in source.
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