确定是否执行了 Server.Transfer[Request]

Question

I was debugging two things and discovered that when an action executed:

Server.TransferRequest(url);
return new EmptyResult();

that my Application_Error would fire and catch the exception "The SessionStateTempDataProvider class requires session state to be enabled."

(I do have session state enabled, specifically StateServer, and for the sake of discussion let's imagine I do not need to commit changes from this request back to the session)

I'd like to control how this scenario gets logged. Obviously I can detect the exception type and message text, but if I wanted to not do special logging when the Request was .TransferRequest 'd (or .Transfer 'd), how can I do this?

I have already examined Response.IsRequestBeingRedirected - it was false .

Answer 1

Each Server.Transfer will add an unsafe request completion call to the stack, therefore, if there are more than 1 of this, you may think that the request is internally redirected by one of the Server.Transfer or Server.TransferRequest methods

Here is a boolean function which you can add to your global.asax file, which will return true if it finds more than one instances of request completion frames in the current stack trace.

The new StackTrace() is an expensive operation, but, because this is executing in an Exceptional context here, it's overhead "may" be ignored.

private bool IsRequestTransferred()
{
    System.Diagnostics.StackTrace stackTrace = new System.Diagnostics.StackTrace();
    int requestCompletionCount = 0;
    foreach (var stackFrame in stackTrace.GetFrames())
    {
        System.Reflection.MethodBase methodBase = stackFrame.GetMethod();
        if (methodBase.DeclaringType.Name == "UnsafeIISMethods" && methodBase.Name == "MgdIndicateCompletion")
        {
            if (++requestCompletionCount == 2)
            {
                return true;
            }
        }
    }
    return false;
}

void Application_Error(object sender, EventArgs e)
{
    bool isRequestTransferred = IsRequestTransferred();
}

Answer 2

Server.TransferRequest accepts headers collection. You can add a special technical header and then look for it later.

Server.TransferRequest(url,
    true,
    method: "GET",
    headers: new NameValueCollection() { { "transferred", "true" } });

//and then
bool isTransferred = (Request.Headers["transferred"] != null);