There are similar questions on Stackoverflow and other websites, but I seem to miss something.
I have a GridView bound to a DataTable which comes from a database. My goa
GridView's in ASP.NET have some built in commands - Deleted, Update, etc. What's happening is that your button has a command name of Update, and the Gridview is hijacking that from you and firing a RowUpdating event instead of your RowEditing event. Change your button command name to be Edit, and use a RowEditing event.