Queryable.SingleOrDefault<'TSource> Method (IQueryable<'TSource>, Expression<Func<'TSource, Boolean>>)
Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
Assembly: System.Core (in System.Core.dll)
static member SingleOrDefault<'TSource> : source:IQueryable<'TSource> * predicate:Expression<Func<'TSource, bool>> -> 'TSource
The single element of the input sequence that satisfies the condition in predicate, or default(TSource) if no such element is found.
The type of the elements of source.
This method has at least one parameter of type Expression<'TDelegate> whose type argument is one of the Func<'T, 'TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<'TDelegate>.
The MethodCallExpression that represents calling 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.method generates a
The query behavior that occurs as a result of executing an expression tree that represents callingdepends on the implementation of the type of the source parameter. The expected behavior is that it returns the only element in source that satisfies the condition specified by predicate, or a default value if no such element exists.
The following code example demonstrates how to useto select the only element of an array that satisfies a condition. The second query demonstrates that returns a default value when the sequence does not contain exactly one element that satisfies the condition.
Available since 8
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Available since 8.1