Form View Firing Update Event in C#

I've inherited a C# ASP.NET web application and I'm trying to add 5 fields onto a FormView.  One of the fields (in a text box) I want to strip out certain characters on when the form view is submitted.  I tried to use the below event (disregard the confusing naming):

    protected void DetailView_ItemUpdating(Object sender, FormViewUpdateEventArgs e)

The problem is, this event never seems to fire.  In the FormView tag I added the OnItemUpdating="DetailView_ItemUpdating" and even tried adding the below to the Page_Load event:

DetailView.ItemUpdating += new EventHandler(DetailView_ItemUpdating);

I've traditionally used VB.Net as my code behind and never experienced issues wiring up these events.  Where am I going wrong trying to get this event to fire or where would be a better place to update the value of that item before it's committed to the database?