This event is the only place in RadGridView API where you can access the final filtering expression as a string. This string value is produced by all items in filtering expressions collection. The expression applies to the whole grid template(single table if hierarchy is used).
[C#] Filter expression changed event
void radGridView1_FilterExpressionChanged(object sender, Telerik.WinControls.UI.FilterExpressionChangedEventArgs e)
e.FilterExpression = "(([ProductName] LIKE '%Qu%'))";
[VB.NET] Filter expression changed event
Private Sub RadGridView1_FilterExpressionChanged(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.FilterExpressionChangedEventArgs)
This event is also the final place where the filtering expression can be changed before it is evaluated.
It is preferable to use the filtering expression objects and modify the filtering string only if you want to access functionality not provided by the filtering expressions API.
If the expression cannot be evaluated, ArgumentException is thrown. The inner exception describes the concrete reason for the problem.