This is the same issue as you already posted at
Error on double click on datagrid in WPF VB.NET[
^]. I have just built the program from your original code, and the corrections provided by @RichardDeeming, and it works correctly. If you still have problems then you need to show the actual code, and explain what happens when you run it. So please use the
Improve question link above, and add complete details.