Multicolumncombobox compositefilter too slow

Hello, Ignacio, 

We already have a similar issue logged in our feedback portal. You can track its progress, subscribe for status changes and add your comments on the following link - feedback item.

Currently, the possible solution that i can suggest is to use custom filtering instead of CompositeFilterDescriptor. A sample approach is demonstrated in the referred feedback item.

I hope this information helps. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Thanks for the reply, I've tried to implement the custom filter on my grid multicolumncombobox but the process is not working as expected. Event is not firing when I write in the cell, it is firing when i click in the cell, it is very strange because I followed the same steps you posted in this link (https://feedback.telerik.com/Project/154/Feedback/Details/176209-fix-radmulticolumncombobox-filtering-performance-and-cursor-lagging)

Thanks anyway! 

Hello, Ignacio, 

I would recommend you to have a look at the following help article demonstrating how the custom filtering works for RadGridView: https://docs.telerik.com/devtools/winforms/gridview/filtering/custom-filtering

You can also refer to our Demo application >> GridView >> Filtering >> Custom Filtering example.
 
If you are still experiencing any further difficulties, feel free to submit a support ticket where you can provide a sample project demonstarting the undesired behavior. Thus, our support staff will gladly assist you.

I hope this information helps. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Finally I could implement the custom filter in my radmulticolumncombobox, but the event customfilter is being called for each line for the grid inside the radmulticolumncombobox. So, when I have 500000 rows to filter, the program is frozen for a long time, well, it doesn't work again.

Hello, Ignacio, 

Indeed, the CustomFiltering event is fired for each row in the popup grid in order to determine whether the row matches the filter criteria or not. However, to be honest, 500 000 rows is a huge number and it is normal to affect the performance in RadGridView. For such case, it is suitable to use a RadVirtualGrid. It is a grid component developed on top of Telerik Presentation Framework which provides a convenient way to implement your own data management operations and optimizes the performance when interacting with large amounts of data. You can refer to the online documentation for getting started experience and how to filter the loaded data on demand: 
https://docs.telerik.com/devtools/winforms/virtualgrid/overview
https://docs.telerik.com/devtools/winforms/virtualgrid/filtering/filtering

You can host the RadVirtualGrid in a RadPopupEditor and thus simulate RadMultiColumnComboBox:
https://docs.telerik.com/devtools/winforms/editors/popupeditor/popupeditor
https://docs.telerik.com/devtools/winforms/editors/popupeditor/getting-started

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik