Problem passing ELMAH log id to Custom Error page in ASP.NET

.net, c#, elmah, visual-studio

Solution

This works for me:

void ErrorLog_Logged(object sender, ErrorLoggedEventArgs args)
{
    if (args.Entry.Error.Exception is HandledElmahException)
        return;

    var config = WebConfigurationManager.OpenWebConfiguration("~");
    var customErrorsSection = (CustomErrorsSection)config.GetSection("system.web/customErrors");        

    if (customErrorsSection != null)
    {
        switch (customErrorsSection.Mode)
        {
            case CustomErrorsMode.Off:
                break;
            case CustomErrorsMode.On:
                FriendlyErrorTransfer(args.Entry.Id, customErrorsSection.DefaultRedirect);
                break;
            case CustomErrorsMode.RemoteOnly:
                if (!HttpContext.Current.Request.IsLocal)
                    FriendlyErrorTransfer(args.Entry.Id, customErrorsSection.DefaultRedirect);
                break;
            default:
                break;
        }
    }        
}

void FriendlyErrorTransfer(string emlahId, string url)
{
    Server.Transfer(String.Format("{0}?id={1}", url, Server.UrlEncode(emlahId)));
}

Problem

I am using ELMAH to log unhandled exceptions in an ASP.NET Webforms application. Logging is working fine. I want to pass the ELMAH error log id to a custom error page that will give the user the ability to email an administrator about the error. I have followed the advice from this answer. Here is my `global.asax` code: ``` void ErrorLog_Logged(object sender, ErrorLoggedEventArgs args) { Session[StateKeys.ElmahLogId] = args.Entry.Id; // this doesn't work either: // HttpContext.Current.Items[StateKeys.ElmahLogId] = args.Entry.Id; } ``` But, on the Custom error page, the session variable reference and HttpContext.Current.Items are giving me a NullReference exception. How can I pass the ID to my custom error page?

Original source

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