Queryable::Where<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Int32, Boolean>>)
Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
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 filter.
- predicate
- Type: System.Linq.Expressions::Expression<Func<TSource, Int32, Boolean>>
A function to test each element for a condition; the second parameter of the function represents the index of the element in the source sequence.
Return Value
Type: System.Linq::IQueryable<TSource>An IQueryable<T> that contains elements from the input sequence that satisfy the condition specified by predicate.
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 or predicate is nullptr. |
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 Where<TSource>(IQueryable<TSource>, Expression<Func<TSource, Int32, Boolean>>) method generates a MethodCallExpression that represents calling Where<TSource>(IQueryable<TSource>, Expression<Func<TSource, Int32, Boolean>>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(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 Where<TSource>(IQueryable<TSource>, Expression<Func<TSource, Int32, Boolean>>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the elements from source that satisfy the condition specified by predicate. The index of each source element is provided as the second argument to predicate.
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