Sometimes Asp.Net Button Fires Event, Sometimes Not?

I'm trying to make a form-check but submit button (asp:Button) sometimes fires target method and sometimes not. I recorded my debugging operation and uploaded it to YouTube, please watch it first to understand what's going on: YouTube Link >>


I'm really confused about it. Is it just about concurrency or what? What to do? Suggestions? Thanks!


Button Code:



<asp:Button ID="RegisterButton" OnClick="Register" Text="Register" CssClass="button" runat="server" />