I have the same problem which I have been fighting with all day and can't work out. I have to click Edit and Cancel twice for them to do their action. The first and second click are calling the ModeChanging method so I assume there is something wrong with my code and the same with justB's code.

If I don't put in the ModeChanging event implementation I get an exception:
"The DetailsView 'dvwWorkItem' fired event ModeChanging which wasn't handled."

I do intend on adding other custom code into this method because certain actions need to happen when you start editing or inserting.

Here is the code I have so far:

protected void dvwWorkItem_ModeChanging(object sender, DetailsViewModeEventArgs e)
    {
        if (e.NewMode == DetailsViewMode.Edit)
        {
            dvwWorkItem.ChangeMode(DetailsViewMode.Edit);
        }
        else if (e.NewMode == DetailsViewMode.ReadOnly)
        {
            if (e.CancelingEdit == true)
            {
                dvwWorkItem.ChangeMode(DetailsViewMode.ReadOnly);
            }
        }
    }

I apprecicate any information anyone has that might be able to solve this problem.
Jono