Can you try the following (assuming the VQCV is the ItemsSource of the grid):
public override void Prepare(Telerik.Windows.Controls.GridViewBoundColumnBase column)
var grid = column.DataControl;
var vqcv = grid.ItemsSource as VirtualQueryableCollectionView;
var filterDescriptors = vqcv.FilterDescriptors;
This should solve the problem?
Just for the record, the grid is not the one that is calling the constructor of your filtering control. In fact you are calling it and then assigning it to the FilteringControl property of the column. Well, sort of. You don't actually see this because you are probably doing this in XAML, but if you were to do the same thing in code-behind it would look like this:
column.FilteringControl = new MyCustomFilteringControl();
Same thing in XAML would look something like this (pseude-code)
However, when defining it in XAML it has to have a default constructor which is then called by the XAML parser. So you can only call non-default constructors in code-behind.
But please use the Prepare method approach that I have described in the beginning of the post.
Let me know if this does not help.
the Telerik team
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