Show Windows Form in native client

andrlage

I'm doing com interop from a native client.
The native client uses a native dll to call managed server dll.
All I want is to display a simple form when it load in my native application.
I really appreciate your help/thoughts on this.

Sincerely
Andla
------------------------------------------------------
This is the server

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Reflection;
using System.Runtime.InteropServices;

namespace Server1
{
[Guid("?????????????????")]
public interface IPelle
{
string ShowPelle();
}

[Guid("?????????????????")]
public class PelleClass : IPelle
{
public string ShowPelle()
{
Form1 test = new Form1();

test.Activate();
System.Threading.Thread.Sleep(5000);
return "Pelle 1 was here";
}
}
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
}
}

This is the client native dll:

        IPellePtr pelleptr;
        HRESULT hr2 = pelleptr.CreateInstance(__uuidof(PelleClass));
        if (SUCCEEDED(hr2))
        {
            MessageBox(0,pelleptr->ShowPelle(),"",0);

        }

10 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
You have to call Form.ShowDialog() from the managed code to ensure it will run on a WF message loop and therefore work correctly.

So, your ShowPelle method will need to be changed to:

public string ShowPelle()
{
Form1 test = new Form1();
test.ShowDialog();
return "Pelle 1 was here";
}

Calling ShowDialog() will, of course, block the thread until the form is closed. So, your string won't be returned until then.
andrlage15y ago
If there is a problem understanding what I want then it is my fault. I find myself unaware from time to time to explain things in the most crappiest manner.

I'm aware that I can run managed code in c++ so why have I not done that. The simple reason because it is Microsoft. They like to change things so that if I take a project and convert it then I need to do a lot of extra work. Well for small demo projects with a few files it is ok to convert but for the current over 15 year old unmanaged c++ big ass project I will not involve myself in fixing all the missing stuff for the upgrade. The other reason is because I want clean understandable easy to debug code = C# (and it rocks!)

Back to this stuff. I think it is a natural process to make the client support a sink when the server starts the window manage form I want to deal with certain events so I want to use source functions to connect to the sink on the client side.

I think I'm going to implement sink functionality because I think it isn't that hard after I found an awesome article with source code to exactly what I'm looking for.
Here is the link:
http://codeguru.earthweb.com/csharp/csharp/cs_misc/com/print.php/c15199__2/

I think this link should be saved on c-sharpconer because it is what many are looking for.

Cheers
Sam Hobbs15y ago
#import makes things easier, but it is not necessary. It imports a type library and generates code. The code includes smart pointers that take care of details for you, such as automatic allocation and de-allocation.

I don't understand what you are using an event sink for. You probably have explained that and if so then I forget. I know that old-style C++ COM is confusing. I hope you figure it out.

There is one point I am not sure you understand. It is possible to use managed code in C++. I am not sure that you are doing that. If not then it might make things easier. And then going the other direction, you can use COM objects much easier in C#. It is not clear to me why you are not doing that; I am sorry that I do not understand if you have explained that.
andrlage15y ago
I suppose I can't use "__uuidof(PelleClass)" without import.
That is what I need to run this?

BTW I'm thinking of skipping eventsink and stuff and instead create my own polling routine.
Is that very amateurish or if you look it another way lot of time saving :)
Don't know. For the information I found it involved much extra work to what? Get some
call back to my functions? Still something tells me I must do things right but I question
the purpose of doing this.
Sam Hobbs15y ago
Your C++ code that you posted is not using a #import. So even if your program has a #import, you are not taking advantage of the conveniences it provides. So you are essentially not using #import and a type library.
andrlage15y ago
Thanks Vulpes it works. So simple and so awesome. I will have to laborate a bit more so I can communicate between the client and server. The modal mode will probably be messing with me.
Thanks again.
andrlage15y ago
I use import and tlb. This is taken care of. There is a lack of articles that handle this. I have really searched for code samples and more information but I couldn't find any.

Vulpes the info you provided was helpful but I'm still stuck. Do I have to use the showdialog in the native c++ in modal mode to make it work?
Not sure how I would do that and how to proceed.

Mahesh Chand
The idea is to move away from C++ / MFC. I want to make a bridge between a native application and c#. If I know how to build the bridge then I don't have to fish around with c++ much any more which is a time waster.
Sam Hobbs15y ago
I am not sure I understand what you are doing but it is likely that there are articles in this web site that can help you.

Is the managed server a COM object? Is there a type library for it? If there is a type library for it then use a "#import" in your C++ program to reduce the details you need to do.

However I am sorry but I don't see a question.
Vulpes15y ago
There are some issues in trying to open a Windows Form from an unmanaged COM client because of fundamental differences between WF and unmanaged message loops. In plain English, they don't work properly!

These problems can be circumvented by always opening the windows form modally (using ShowDialog), so that it will run on a WF message loop, and by opening it on a new thread.

Please see this MSDN article (http://msdn.microsoft.com/en-us/library/ms229600.aspx) for more details.
Mahesh Chand15y ago
When you say, native, does that mean C++? You can use C++ Window class Wnd or MFC for this. Jeez, I did this 13 years ago.