Global.asax file of the Web application to capture the error and redirect the user to a custom error page. The Application_Error method may appear similar to one of the following code examples.

protected void Application_Error(Object sender, EventArgs e)
{
// Code that runs when an unhandled error occurs.
// Determine whether the request originates from the file upload Web page (FileUpload.aspx).
if (Request.Path.EndsWith("FileUpload.aspx "))
{

// Obtain the error details.
HttpException httpEx = Server.GetLastError() as HttpException;

// Verify the expected error.
if (httpEx.GetHttpCode() == 500 && httpEx.ErrorCode == -2147467259)
{
Server.ClearError();

// Redirect the user to the custom error page (ErrorPage.aspx).
HttpContext.Current.Response.Redirect("ErrorPage.a spx");
}
}
}