Managed C++ and Windows Forms

Introduction

One big complaint I have about Visual Studio .NET is that it does not support a GUI designer tool for Managed C++. Its not going to be easy to design a heavily-GUI oriented program in Managed C++. But then we can always try.  In this article I'll try and give an introduction to using Windows Forms in your Managed C++ applications.

Lets jump straight into our first program. Use the App Wizard to generate a basic Managed C++ application for you. I used the name sample01 for my project and so my main file is sample01.cpp. In your case this filename will depend on the name you chose for your project. Make the required changes to your cpp source so that you have a file looking like the listing below.

Program 1

#include "stdafx.h"

#using <mscorlib.dll>
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Drawing;
using namespace System::Windows::Forms;

//we derive a class from the Form class
//notice how we don't need any header files
__gc class MyForm : public Form
{
};

int __stdcall WinMain()
{
    //this will start a message loop for our form	
    Application::Run(new MyForm());
    return 0;
}

Well, as you can see, I have made several changes to the App wizard generated code. First I have added all those dll references and their corresponding namespace references. I have added a new managed class called MyForm which is derived from System::Windows::Forms::Form.

I have replaced wmain with WinMain so that we won't have to see that ugly console window behind our beautiful Form. I have prefixed it with __stdcall otherwise you'll see a warning. That's how the Win 32 API has defined WinMain(). Then we have used the static function Run of the Application class. This will start the standard application message loop.

Well, go ahead. Build and run it. You'll see your first Windows Form. Use Ctrl-F5 to run it. If you click on the play button the program will run in debug mode which is considerably slower.

Program 2

#include "stdafx.h"

#using <mscorlib.dll>
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Drawing;
using namespace System::Windows::Forms;

//we derive a class from the Form class
//notice how we don't need any header files
__gc class MyForm : public Form
{
public:
    MyForm();	
    Label *m_label;
};

int __stdcall WinMain()
{
    //this will start a message loop for our form
    Application::Run(new MyForm());
    return 0;
}

MyForm ::MyForm()
{
    //set some form properties/fields
    this->Text = "Elmer Fudd";
    this->FormBorderStyle=FormBorderStyle::Fixed3D;
    this->MaximizeBox=false;
    this->ClientSize=System::Drawing::Size(400,300);

    //create the Label object and set its properties/fields
    m_label=new Label();
    m_label->Text="Keep wewy wewy quiet. I am huntin wabbit";
    m_label->Size=System::Drawing::Size(300,50);
    m_label->Location=Point(5,5);	

    //add the label to the form
    this->Controls->Add(m_label);
}

Well, now we have made several changes more. We have added a Label member to our Form derived class and also a constructor. In the constructor we set some properties and fields of our form. We give it a title. We fix its border and make it non-sizable. We disable the maximize box. And also set its size.

We then create our Label object and set its text, size and location. Then we add the label to the form by adding it to the form's controls collection. Build and run it. You should see a more lively window now that, it has a title and some text on it.

Program 3

#include "stdafx.h"

#using <mscorlib.dll>
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Drawing;
using namespace System::Windows::Forms;

//we derive a class from the Form class
//notice how we don't need any header files
__gc class MyForm : public Form
{
public:
    MyForm();	
    Label *m_label;
    Button *btn;
    TextBox *txt1;
    void btn_Click(Object *sender, System::EventArgs* e);
};

int __stdcall WinMain()
{
    //this will start a message loop for our form
    Application::Run(new MyForm());
    return 0;
}

MyForm ::MyForm()
{
    //set some form properties/fields
    this->Text = "Elmer Fudd";
    this->FormBorderStyle=FormBorderStyle::Fixed3D;
    this->MaximizeBox=false;
    this->ClientSize=System::Drawing::Size(400,300);

    //create the Label object and set its properties/fields
    m_label=new Label();
    m_label->Text="Keep wewy wewy quiet. I am huntin wabbit";
    m_label->Size=System::Drawing::Size(300,50);
    m_label->Location=Point(5,5);	

    //add the label to the form
    this->Controls->Add(m_label);

    btn=new Button();
    btn->Text="Click me dude!";
    btn->Location=Point(5,90);
    btn->Size=System::Drawing::Size(100,22);
    btn->add_Click(new EventHandler(this,&MyForm::btn_Click));

    //add the button
    this->Controls->Add(btn);

    txt1=new TextBox();
    txt1->ReadOnly=true;
    txt1->Size=System::Drawing::Size(200,22);
    txt1->Location=Point(130,90);

    //add the text box
    this->Controls->Add(txt1);
}

//the event handler for button click
void MyForm::btn_Click(Object *sender, System::EventArgs *e)
{
    //we show the current date/time in the text box
    DateTime dt=System::DateTime::Now;
    txt1->Text=dt.ToString();
}

Well, now we have added a button, a text box and an event handler for the button. We have written our btn_Click member function using the expected parameters of the delegate that is associated with the click event. We use add_Click to add our event handler to the list of functions that get notified of the event. And as you can see, in the handler we have written code to put the current date and time into the text box.

Build and run the program. You'll see that each time you click the button, the text box gets updated with the current date and time. Easy, huh?

Conclusion

You can build more complex programs but the basic idea is the same. Event handling is done via virtual functions which you can override. But I still have a faint hope that when Microsoft finally releases the next version of VS.NET, they'll have a CodeDOM like gadget for Managed C++.

Thank You