Re: A complex one..... - C# Discussion Boards

27-Apr-03 5:40

...
Prepare for confusion, but please help.

I have a plugin framework, using reflection.
This works brilliantly and I will release the code eventually. However, one of the plugins is calling an async callback. This throws an invokation exception:

Cannot load type GoogleSearch.GoogleSearchForm, GoogleSearch, Version=1.0.1212.26393, Culture=neutral,<br> PublicKeyToken=null.    at System.Runtime.Remoting.Messaging.MethodCall.ResolveMethod(Boolean bThrowIfNotResolved)
   at System.Runtime.Remoting.Messaging.MethodCall.ResolveMethod()
   at System.Runtime.Remoting.Messaging.MethodCall..ctor(IMessage msg, Boolean needAccessCheck)
   at System.Runtime.Remoting.Proxies.AgileAsyncWorkerItem..ctor(IMethodCallMessage message, AsyncResult ar, Object target)
   at System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(Object NotUsed, MessageData& msgData)
   at GoogleSearch.SearchDelegate.BeginInvoke(String url, String& result, AsyncCallback callback, Object object)
   at GoogleSearch.GoogleSearchForm.search_Click(Object sender, EventArgs e) <br>in c:\documents and settings\administrator.jonny\my documents\visual studio projects\screenmate\googlesearch\google.cs:line 219
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.ComponentManager.System.Windows.Forms.UnsafeNativeMethods<br>+IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.RunDialog(Form form)
   at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
   at System.Windows.Forms.Form.ShowDialog()
   at GoogleSearch.GooglePlugin.LoadGoogleForm()<br> in c:\documents and settings\administrator.jonny\my documents\visual studio projects\screenmate\googlesearch\google.cs:line 36

Now, let me tell you how the app works. The main app gets methods via reflection. And in the end get to this point:

object o = Activator.CreateInstance(t);
// t being the type in question - all correct
MethodInfo mi2 = t.GetMethod("AcceptRect");
Rectangle rect = new Rectangle(this.Location,this.Size);
mi2.Invoke(o,new object[]{rect});

Now that works fine on all plugins, including the troublesome one.
Now in the plugin class, there is a call to another class in the plugin dll. One based on a windows form. The form loads ok.

A button on the form starts an async callback to process some data. NOW THIS DOESN'T WORK.

GoogleSearch.GoogleSearchForm gs = new GoogleSearch.GoogleSearchForm(this.bob);
gs.ShowDialog();

The above opens the form. (This is all within the same dll and namespace)

// the folowing is the call in the buttons click handler

SearchDelegate search = new SearchDelegate(this.Search);
string result;
search.BeginInvoke(url, out result, new AsyncCallback(this.AnnounceSearch),search);


// the following is the delegate decleration
public delegate string SearchDelegate(string url, out string result);



public string Search(string url, out string result)
{
ArrayList ar = new ArrayList();
			
Uri uri = new Uri(url);

WebRequest wr = WebRequest.Create(uri);
WebResponse resp = wr.GetResponse();
Stream s = resp.GetResponseStream();
StreamReader sr = new StreamReader(s);

string t = sr.ReadToEnd();

sr.Close();
return (result = t);
}

public void AnnounceSearch(IAsyncResult iar)
{
SearchDelegate search = (SearchDelegate)iar.AsyncState;
			
string result;
search.EndInvoke(out result, iar);
this.panel1.Controls.Clear();

//this must be invoked because it is adding controls to a form, and needs to be done in the parent thread
MakeControlsDelegate del = new MakeControlsDelegate(MakeControls);
this.Invoke(del,new object[]{result});
}

public delegate void MakeControlsDelegate(string t);

public void MakeControls(string t)
{

ArrayList gr = this.ParseGoogle(t);

foreach(LinkLabel ll in gr)
{
this.panel1.Controls.Add(ll);
}

Ok, I think thats everything now...

Anyway, the above code WORKED PERFECTLY when it was not a plugin and was just a compile time dll.

The only thing i've changed is the fact that the form is being run from a late-binding dll.

"If you just say porn then you get all manner of chaff and low grade stuff."
- Paul Watson, Lounge 25 Mar 03
"If a man is standing in the middle of the forest speaking and there is no woman around to hear him, is he still wrong?"
- Anon

Jonathan 'nonny' Newman
Homepage [www.nonny.com] [^]

leppie27-Apr-03 6:20

27-Apr-03 6:20

You are likely having a threading issue. Try as the AsyncCallback is invoked from another thread. Do the following:

from your control:

Invoke(mi.Invoke, new object[]{o, new object[]{rect}});

Eek. Dunno if that will work, but give it a try Smile | :)

I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02

Jon Newman27-Apr-03 6:31

27-Apr-03 6:31

I'm not sure I understand where i'm to place that.

The plugin is activated and invoked from a form in the main app and main thread.

From the new instance of the plugin, the plugin class loads the plugin form.

object o = Activator.CreateInstance(t);
MethodInfo mi = t.GetMethod("SomeMethod");
mi.Invoke(o,null);

does the above code create the instance of the object in a new thread, or the same thread as the method that runs it?

Jonathan 'nonny' Newman
Homepage [www.nonny.com] [^]

leppie27-Apr-03 7:19

27-Apr-03 7:19

Jonny Newman wrote:
does the above code create the instance of the object in a new thread, or the same thread as the method that runs it?

That will create the object in the calling thread.

I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02

James T. Johnson27-Apr-03 13:03

James T. Johnson

27-Apr-03 13:03

Jonny Newman wrote:
Anyway, the above code WORKED PERFECTLY when it was not a plugin and was just a compile time dll.

The only thing i've changed is the fact that the form is being run from a late-binding dll.

Just judging from that I would say there is a problem with the application resolving assemblies.

In the FrameworkSDK\bin directory (located within VS.NET's install folder) you'll find FUSLOGVW.exe which will let you see what the runtime is trying to do to find the assemblies it needs to load.

Run that, make sure you check the "Log Failures" checkbox, then run your application. You should see where it is expecting to find the assemblies it is loading, and if it fails to load an assembly the plugin depends on.

HTH,

James

"It is self repeating, of unknown pattern"
Data - Star Trek: The Next Generation

Jon Newman27-Apr-03 13:46

27-Apr-03 13:46

The operation failed.
Bind result: hr = 0x80070002. The system cannot find the file specified.

Assembly manager loaded from:  C:\WINNT\Microsoft.NET\Framework\v1.0.3705\fusion.dll
Running under executable  C:\Documents and Settings\Administrator.JONNY\My Documents\Visual Studio Projects\ScreenMate\ScreenMate\bin\Debug\ScreenMate.exe
--- A detailed error log follows. 

=== Pre-bind state information ===
LOG: DisplayName = GoogleSearch, Version=1.0.1212.29205, Culture=neutral, PublicKeyToken=null
 (Fully-specified)
LOG: Appbase = C:\Documents and Settings\Administrator.JONNY\My Documents\Visual Studio Projects\ScreenMate\ScreenMate\bin\Debug\
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = NULL
Calling assembly : (Unknown).
===

LOG: Processing DEVPATH.
LOG: DEVPATH is not set. Falling through to regular bind.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Post-policy reference: GoogleSearch, Version=1.0.1212.29205, Culture=neutral, PublicKeyToken=null
LOG: Attempting download of new URL file:///C:/Documents and Settings/Administrator.JONNY/My Documents/Visual Studio Projects/ScreenMate/ScreenMate/bin/Debug/GoogleSearch.DLL.
LOG: Attempting download of new URL file:///C:/Documents and Settings/Administrator.JONNY/My Documents/Visual Studio Projects/ScreenMate/ScreenMate/bin/Debug/GoogleSearch/GoogleSearch.DLL.
LOG: Attempting download of new URL file:///C:/Documents and Settings/Administrator.JONNY/My Documents/Visual Studio Projects/ScreenMate/ScreenMate/bin/Debug/GoogleSearch.EXE.
LOG: Attempting download of new URL file:///C:/Documents and Settings/Administrator.JONNY/My Documents/Visual Studio Projects/ScreenMate/ScreenMate/bin/Debug/GoogleSearch/GoogleSearch.EXE.
LOG: All probing URLs attempted and failed.

Well, it seems to state that the dll was never loaded.
However, the dll must have been loaded because the form the button is on is in that dll, code is actually being run from it. It is definately something to do with the async callback.

Should I try starting the Activator.CreateInstance() in another thread?

Threading isn't my strong point.

Jonathan 'nonny' Newman
Homepage [www.nonny.com] [^]

Mark Smithson27-Apr-03 21:43

Mark Smithson

27-Apr-03 21:43

I don't think your problem has to do with threading. It doesn't matter on which thread you are trying to create the object, the CLR cannot find the assembly file that the object is defined in.

Which files do you have as part of your application? Presumably you have an application exe and the GoogleSearch.dll is the plugin.

Is the GoogleSearch dll located at any of the locations in the output above? If so is the dll of the same version listed above (i.e. 1.0.1212.29205)?

Regards

Mark Smithson

Jon Newman28-Apr-03 5:51

28-Apr-03 5:51

googlesearch.dll is located in the /plugin directory. But I don't see how this causes a problem since the plugin is already loaded and working, so the file location shouldn't matter, but obviously if its looking in the wrong place for it then there must be a problem.

On the point of asyncs. Would it help if I made the async methods static, might this help resolve stuff?

Jonathan 'nonny' Newman
Homepage [www.nonny.com] [^]

Mark Smithson28-Apr-03 8:10

Mark Smithson

28-Apr-03 8:10

I'm not really sure what you mean by 'loaded and working'. You code and the errors imply that the CLR cannot load a type.

This is because your plugin directory is not in the probing path for the application. Your will either need to change your applications config file to include this directory, or manually load the assemblies.

Try adding the following to your app.config file

<configuration>
   <runtime>
      <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
         <probing privatePath="plugins"/>
      </assemblyBinding>
   </runtime>
</configuration>

Also have a look at the following MSDN link for further information on the how the CLR locates assemblies

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconhowruntimelocatesassemblies.asp

Regards

Mark Smithson

Jon Newman28-Apr-03 11:53

28-Apr-03 11:53

Cheers that seems to have done the trick! I knew it would be simple Smile | :)

Jonathan 'nonny' Newman
Homepage [www.nonny.com] [^]

Marshalling char**

leppie27-Apr-03 2:42

27-Apr-03 2:42

Hi all (and S.Rod. as you are most likely to answer this Smile | :)

)

Say I have a C function:

char** Foo(int* size);

Now in MC++ its pie and I can just go:

int size = 0;
char** buffer = Foo(&size);
String* results __gc[] = new String*[size];
for (int i = 0; i < size; i++)
{
  results[i] = new String(buffer[i]);
  free(buffer[i]);
}
free(buffer);

But how do I approach this from a Marshalling POV in C# given I have Foo as a DllImport defined as IntPtr Foo(out int size)? How do I access the individual char* and the finally free the returned IntPtr? My attempts has failed miserably Frown | :(

Thanks

I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02

Stephane Rodriguez.27-Apr-03 7:25

Stephane Rodriguez.

27-Apr-03 7:25

Here is how I got it to work,

C implementation :

extern "C" __declspec(dllexport) char** foo(int *nSize);

// implementation
__declspec(dllexport) char** foo(int *nSize)
{
  *nSize = 2;
  ::MessageBox(NULL,"unmanaged foo call","message",MB_OK);

  char **lpstr = (char**) CoTaskMemAlloc( 2*sizeof(LPSTR) );
  lpstr[0] = (char*) CoTaskMemAlloc( 100 ) ;
  strcpy(lpstr[0], "string1");
  lpstr[1] = (char*) CoTaskMemAlloc( 100 ) ;
  strcpy(lpstr[1], "string2");

  return lpstr;
}

Now for the managed part,

// declaration
[DllImport(@"..\bin\foo.dll", CharSet=CharSet.Auto)]
static public extern IntPtr foo(ref int nSize); // 

// implementation
int nSize = 0;
IntPtr pData = foo(ref nSize);
for (int i=0; i<nSize; i++)
{
  IntPtr pString = Marshal.ReadIntPtr(pData, 4*i);
  MessageBox.Show( Marshal.PtrToStringAnsi(pString) );
}

leppie27-Apr-03 7:59

27-Apr-03 7:59

.S.Rod. wrote:
Marshal.ReadIntPtr

Dope, how did I miss that one again (some bells ring)? PtrToStringAnsi frees the string, would FreeHGlobal(pData) at the end be right then?

Thanks for the reply Smile | :)

I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02

Stephane Rodriguez.27-Apr-03 8:05

Stephane Rodriguez.

27-Apr-03 8:05

FreeCoTaskMem(pData);

leppie27-Apr-03 8:42

27-Apr-03 8:42

Hmm, I allocated the unmanaged memory with calloc, is FreeHGlobal an alias for that or do i need to dllimport that?

I rated this article 2 by mistake. It deserves more. I wanted to get to the second page... - vjedlicka 3:33 25 Nov '02