Queryable::Single<TSource> Method (IQueryable<TSource>)
Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Linq::IQueryable<TSource>
An IQueryable<T> to return the single element of.
Return Value
Type: TSourceThe single element of the input sequence.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<TSource>. When you use instance method syntax to call this method, omit the first parameter.| Exception | Condition |
|---|---|
| ArgumentNullException | source is nullptr. |
| InvalidOperationException | source has more than one element. |
The Single<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Single<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 Single<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the only element in source.
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