DDE in .NET

Someone recently made me remind an old technology called DDE.

“Dynamic Data Exchange (DDE) is a technology for communication between multiple applications under Microsoft Windows or OS/2”

“The primary function of DDE is to allow Windows applications to share data. For example, a cell in Microsoft Excel could be linked to a value in another application and when the value changed, it would be automatically updated in the Excel spreadsheet. The data communication was established by a simple, three-segment model. Each program was known to DDE by its "application" name. Each application could further organize information by groups known as "topic" and each topic could serve up individual pieces of data as an "item". For example, if a user wanted to pull a value from Microsoft Excel which was contained in a spreadsheet called "Sheet1" in the cell in the first row and first column, the application would be "Excel", the topic "Sheet1" and the item "r1c1".

Note: In DDE, the application, topic and item are not case-sensitive.”

So in VB6 you can have something like:

Private Sub Form_Load()
Text1.LinkMode = 0
Text1.LinkTopic = "Excel|Sheet1"
Text1.LinkItem = "R1C1"
Text1.LinkMode = 1
End Sub

How can you do that in .NET. Is it possible in C#? Well I started looking around and found several forums explaining about all the API calls and I was just about to write my own solution when I found NDDE. This project hosted in CodePlex “provides a convenient and easy way to integrate .NET applications with legacy applications that use Dynamic Data Exchange (DDE)” :)

So this is a  nice example of how to do the previous lines in C#:

        //This class provides the infraestructure for DDE comunication
        NDde.Client.DdeClient ddeClient_TextBox1 = null;

        private void Form1_Load(object sender, EventArgs e)
        {
            //I initialize the DDEClient object. Application is Excel and Topic is Sheet1. I'm using the 
            //the TextBox as the syncronization object
            ddeClient_TextBox1 = new NDde.Client.DdeClient("Excel", "Sheet1", textBox1);
            //Connect to the DDE Server
            ddeClient_TextBox1.Connect();
            //Start the Advise Loop
            ddeClient_TextBox1.StartAdvise("R1C1", 1, true, 60000);
            //Setup the Advise Method
            ddeClient_TextBox1.Advise += new EventHandler<NDde.Client.DdeAdviseEventArgs>(ddeClient_TextBox1_Advise);
            //Setup a method to Poke the Server for TextBox cahnges
            textBox1.TextChanged += new EventHandler(textBox1_TextChanged);

        }
        
        void textBox1_TextChanged(object sender, EventArgs e)
        {
            //Syncronous Poking the server
            ddeClient_TextBox1.Poke("R1C1", textBox1.Text + "\0", 4000);
        }

        const string DDE_postFix = "\r\n\0";
        void ddeClient_TextBox1_Advise(object sender, NDde.Client.DdeAdviseEventArgs e)
        {
            //Advise only if needed
            if (e.Text.Length >=DDE_postFix.Length && textBox1.Text + DDE_postFix != e.Text)
                textBox1.Text = e.Text.Substring(0,e.Text.Length-3);
        }

NOTE: Remember that you need to download NDDE and add a reference to this library

This is very good library, you can also set up a lot of Async calls to even improve performance. I have even thought of making an extender as the ToolTip control to add LinkTopic, LinkMode and LinkItem properties for Winforms controls or provide extensions methods to make all the syntax easier, but that is for a future post. Good Luck.

Migration of ActiveX UserDocuments to C# or .NET

This post describes an an interesting workaround that you can use to support the migration of ActiveX Documents with the Artinsoft Visual Basic Upgrade Companion which is one of the Artinsoft \ Mobilize.NET tools you can use to modernize your Visual Basic, Windows Forms and PowerBuilder applications.

Currently the Visual Basic Upgrade Companion does not allow you to process ActiveX Document directly, but there is a workaround: in general ActiveX Document are something really close to an User Control which is a element that is migrated automatically by the Visual Basic Upgrade Companion.

This post provides a link to a tool (DOWNLOAD TOOL) that can fix your VB6 projects, so the Visual Basic Upgrade Companion processes them. To run the tool:

1) Open the command prompt

2) Go to the Folder where the .vbp file is located

3) Execute a command line command like:

 FixUserDocuments Project1.vbp

This will generate a new project called Project1_modified.vbp. Migrate this new project and now UserDocuments will be supported.

VB6 allows you to create UserDocuments, which can be embedded inside an ActiveX container. The most common one is Internet Explorer. After compilation, the document is contained in a Visual Basic Document file (.VBD) and the server is contained in either an .EXE or .DLL file. During development, the project is in a .DOB file, which is a plain text file containing the definitions of the project’s controls, source code, and so on.

If an ActiveX document project contains graphical elements that cannot be stored in text format, they will be kept in a .DOX file. The .DOB and .DOX files in an ActiveX document project are parallel to the .FRM and .FRX files of a regular Visual Basic executable project. 

The trick to support ActiveX documents is that in general they are very similar to UserControls, and .NET UserControls can also be hosted in a WebBrowser. The following command line tool can be used to update your VB6 projects. It will generate a new solution where UserDocuments will be defined as UserControls.

If you have an ActiveX document like the following: 

Then after running the tool you will have an Project like the following:

So after you have upgraded the projet with the Fixing tool, open the Visual Basic Upgrade Companion  and migrate your project.

After migration you will get something like this:

To use your migrated code embedded in a Web Browser copy the generated assemblies and .pdb to the directory you will publish:

Next create an .HTM page. For example UserDocument1.htm

The contents of that page should be something like the following:

 Now all that is left is to publish the output directory.
To publish your WinForms user control follow these steps.

2. A Wizard to create a Virtual Directory will appear.

 Click Next

 Name the directory as you want. For example Project1. Click Next

 Select the location of your files. Click the Browse button to open a dialog box where you can select your files location. Click Next

 Check the read and run scripts checks and click next

 Now Click Finish

3. Properties for the Virtual Directory will look like this:

NOTE: to see this dialog right click over the virtual directory

4. Now just browse to the address lets say http:\\localhost\Project1\UserDocument1.htm

 And that should be all! :)

The colors are different because of the Host configuration however a simple CSS like:

<style>

 body {background-color: gray;}

</style>

Can make the desired change:

Notice that there will be security limitations, for example for thinks like MessageBoxes.

You can allow restricted operations by setting your site as a restricted site:

For example:

Restrictions

The constraints for this solution include:

* This solutions requires Windows operating system on the client side

* Internet Explorer 6.0 is the only browser that provides support for this type of hosting

* It requires .NET runtime to be installed on the client machine.

* It also requires Windows 2000 and IIS 5.0 or above on the server side

Due to all of the above constraints, it might be beneficial to detect the capabilities of the client machine and then deliver content that is appropriate to them. For example, since forms controls hosted in IE require the presence of the .NET runtime on the client machine, we can write code to check if the client machine has the .NET runtime installed. You can do this by checking the value of the Request.Browser.ClrVersion property. If the client machine has .NET installed, this property will return the version number; otherwise it will return 0.0.

Adding a script like:

<script>

 if ((navigator.userAgent.indexOf(".NET CLR")>-1))

 {

      //alert ("CLR available " +navigator.userAgent);

 }

  else

      alert(".NET SDK/Runtime is not available for us from within " +            "your web browser or your web browser is not supported." +            " Please check with http://msdn.microsoft.com/net/ for " +            "appropriate .NET runtime for your machine.");

</script>

Will help with that.

 References:

ActiveX Documents Definitions:

http://www.aivosto.com/visdev/vdmbvis58.html

Hosting .NET Controls in IE

http://www.15seconds.com/issue/030610.htm