Upload a .ipa-file with c# fileupload

Hey together,

i want to have a upload area for apps(iPhone) in a ASP.NET page. The .plist file is no problem, but when i want to upload the .ipa file, the browser shows 'Webpage not found'.

<asp:FileUpload ID="FileUpload_App" runat="server" /><br />
<asp:Button ID="Button_AddAppUpload" runat="server" Text="Add App" OnClick="Button_AddAppUpload_OnClick" />

public String tempApps = "someString";
protected void Button_AddAppUpload_OnClick(object sender, EventArgs e)
{
  if (FileUpload_App.HasFile)
    {
       FileUpload_App.PostedFile.SaveAs(tempApps + FileUpload_App.FileName);//breakpoint
    }
}

I don´t have any idea, can someone help me and explain this behavior to me? Is it the fileupload causing my problem or is it the ipa-file itself, cause the breakpoint in the method Button_AddAppUpload_OnClick is not reached.

Tags: C#, Mobile Apps (iPhone), ASP.NET