aspcompat performance issue

Question

I am using aspcompat page attribute in ASP.NET so the com components I call can get at ASP intrinsic objects (Request, Response, Application, etc)

I have quickly created a new test project, one asp.net page and a vb6 com component.

The page does this:

for (int i = 0; i < 1000; i++)
   Application["string" + i] = i.ToString();
  Debug.WriteLine(string.Format("{0} done adding strings to app",Environment.TickCount));
  var asp = new ASPTest.CompClass();
  asp.SetProcessId();

Basically I add stuff in the application object and then call the com component.

Set context = GetObjectContext
If Not context Is Nothing Then
    Set app = context("Application")
    Set ses = context("Session")
    Set resp = context("Response")
    If Not app Is Nothing Then
        OutputDebugString "" & GetTickCount & " writing response"
        resp.Write "I see application from vb <br/>"
        OutputDebugString "" & GetTickCount & " before "
        For i = 100 To 200
            resp.Write GetTickCount & " i = " & app("string" & i) & "<br/>"
        Next
        OutputDebugString "" & GetTickCount & " after "
    End If
Else
    OutputDebugString "No context"
End If

The problem is that the more stuff I put in the application the slower the vb code becomes. Not all the code though, just when I first try to invoke any method on intrinsic objects, in my example my first resp.Write call. If I add 10000 items in the app resp.Write takes ten seconds to complete, 60000 => timeout.

It seems that when I touch any intrinsic object the first time the runtime does something nasty to make the objects available to COM.

Have you ever seen this? Any suggestion is much appreciated.

Answer 1

This is almost certainly a problem with threading, probably having the Interop performing thread context switches with every call from the VB component to the classes in the context.

I'm not the expert here, so I might (probably wil) get corrected, but I believe you need to make sure your VB component is also STA, just like the ASP.NET page marked with the aspcompat=true sets it. If you keep all the components in the same thread, there won't be any context switches (which require very expensive marshalling).