Queryable.Count(TSource) Method (IQueryable(TSource), Expression(Func(TSource, Boolean)))
Returns the number of elements in the specified sequence that satisfies a condition.
Assemblies: System.Linq.Queryable (in System.Linq.Queryable.dll)
System.Core (in System.Core.dll)
static member Count : source:IQueryable<'TSource> * predicate:Expression<Func<'TSource, bool>> -> int
The type of the elements of source.
Return ValueType: System.Int32
The number of elements in the sequence that satisfies 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.