Queryable::LongCount<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Boolean>>)
Returns an Int64 that represents the number of elements in a sequence that satisfy a condition.
Assembly: System.Core (in System.Core.dll)
[ExtensionAttribute] public: generic<typename TSource> static long long LongCount( IQueryable<TSource>^ source, Expression<Func<TSource, bool>^>^ predicate )
The type of the elements of source.
Return ValueType: System::Int64
The number of elements in source that satisfy the condition in the predicate function.
Usage NoteIn Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<>. 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).
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 method generates a 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.
The query behavior that occurs as a result of executing an expression tree that represents calling depends on the implementation of the type of the source parameter. The expected behavior is that it counts the number of items in source that satisfy the condition specified by predicate and returns an Int64.
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.