Hello Priyam,

Thank you for posting in our forum.

You may show your user control in BeforeDropDown event of UltraComboEditor and then cancel the event. This will suppress the showing of the default dropdown. You can use code like this:

private void UltraComboEditor_BeforeDropDown(object sender, CancelEventArgs e)

{

    // Add your custom logic here to show your user control

    e.Cancel = true;

}

Please let me know if you have any additional questions.

Thank you for using Infragistics Controls.