Creating an ActiveX control in .Net using C#

Create a new Class Library project in Visual Studio 2010

* This post is taken from: Creating an ActiveX control in .Net using C# by Olav Aukan

1. Start-Run-devenv or Click- Microsoft Visual Studio 2010.
2. After starting Visual Studio click File – New – Project and select Class Library under C#.
3. Call the project ‘AxControls’ and click OK.

Class

Create a new class that inherits from UserControl

1. Rename ‘Class1.cs’ to “HelloWorld.cs”, making sure to rename the class name as well.
2. Add a project reference to System.Windows.Forms.

Reference

Create a new interface that exposes the controls methods and properties to COM interop

1. Right click the project in Visual Studio and click Add –> New Item.
2. Select ‘Interface’ from the list of components, name it ‘IHelloWorld.cs’ and click Add.

iHelloWorld

3.  Edit the ‘IHelloWorld.cs’ file so it looks like this:

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace AxControls
{
    [ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    [Guid("E66C39CB-BB8B-4738-AA0E-5E0D1F2DB230")]
    public interface IHelloWorld
    {
        string GetText();
    }
}
[ComVisible(true)] makes the interface visible to COM.
[Guid("E66C39CB-BB8B-4738-AA0E-5E0D1F2DB230")] let's us manually assign a GUID to the interface. Use guidgen.exe to generate your own.

Make the control class implement the new interface

Make the HelloWorld class implement the IHelloWorld interface and have the GetText() method return a string of your choice. This is what the file might look like:

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace AxControls
{
    [ComVisible(true)]
    [ClassInterface(ClassInterfaceType.None)]
    [Guid("D100C392-030A-411C-92B6-4DBE9AC7AA5A")]
    [ProgId("AxControls.HelloWorld")]
    [ComDefaultInterface(typeof(IHelloWorld))]
    public class HelloWorld : UserControl, IHelloWorld
    {
        #region IHelloWorld Members
        public string GetText()
        {
            return "Hello ActiveX World!";
        }
        #endregion
    }
}

Mark the control as safe for scripting and initialization

By default IE will not allow initializing and scripting an ActiveX control unless it is marked as safe. This means that we won’t be able to create instances of our ActiveX class with JavaScript by default. We can get around this by modifying the browser security settings, but a more elegant way would be to mark the control as safe. Before you do this to a “real” control, be sure to understand the consequences. . We will mark the control as safe by implementing the IObjectSafety interface.

1. Right click the project in Visual Studio and click Add -> New Item.
2. Select ‘Interface’ from the list of components, name it ‘IObjectSafety.cs’ and click Add.

iObjectSafety

3.   Edit the ‘IObjectSafety.cs’ file so it looks like this:

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace AxControls
{
    [ComImport()]
    [Guid("51105418-2E5C-4667-BFD6-50C71C5FD15C")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    interface IObjectSafety
    {
        [PreserveSig()]
        int GetInterfaceSafetyOptions(ref Guid riid, out int pdwSupportedOptions, out int pdwEnabledOptions);
        [PreserveSig()]
        int SetInterfaceSafetyOptions(ref Guid riid, int dwOptionSetMask, int dwEnabledOptions);
    }
}
4.  Make the HelloWorld class implement the IObjectSafety interface. The end result should look something like this:
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace AxControls
{
    [ComVisible(true)]
    [ClassInterface(ClassInterfaceType.None)]
    [Guid("D100C392-030A-411C-92B6-4DBE9AC7AA5A")]
    [ProgId("AxControls.HelloWorld")]
    [ComDefaultInterface(typeof(IHelloWorld))]
    public class HelloWorld : UserControl, IHelloWorld, IObjectSafety
    {
        #region IHelloWorld Members
        public string GetText()
        {
            return "Hello ActiveX World!";
        }
        #endregion
        #region IObjectSafety Members
        public enum ObjectSafetyOptions
        {
            INTERFACESAFE_FOR_UNTRUSTED_CALLER = 0x00000001,
            INTERFACESAFE_FOR_UNTRUSTED_DATA = 0x00000002,
            INTERFACE_USES_DISPEX = 0x00000004,
            INTERFACE_USES_SECURITY_MANAGER = 0x00000008
        };

        public int GetInterfaceSafetyOptions(ref Guid riid, out int pdwSupportedOptions, out int pdwEnabledOptions)
        {
            ObjectSafetyOptions m_options = ObjectSafetyOptions.INTERFACESAFE_FOR_UNTRUSTED_CALLER | ObjectSafetyOptions.INTERFACESAFE_FOR_UNTRUSTED_DATA;
            pdwSupportedOptions = (int) m_options;
            pdwEnabledOptions = (int) m_options;
            return 0;
        }
        public int SetInterfaceSafetyOptions(ref Guid riid, int dwOptionSetMask, int dwEnabledOptions)
        {
            return 0;
        }
        #endregion
    }
}

Create a .msi installer for the control

Before an ActiveX control can be used it must be installed and registered on the client. This can be done in a number of ways, from manually editing the registry to using regasm.exe, but we’re going to create a Vistual Studio setup project to handle the installation for us.

1. Right click the Visual Studio solution, select Add -> New Project and select Setup Project under Other Project Types.
2. Call the project ‘AxControlsInstaller’ and click OK.

AxControlsInstaller

3.        Right click the ‘AxControlsInstaller’ project, select Add -> Project Output, select ‘Primary output’ from the ‘AxControls’

Primary Output

project and Click ‘OK’.

1. Right click ‘Primary output from AxControls (Active)’ and select Properties.
2. Change the Register property from ‘vsdrpDoNotRegister’ to ‘vsdrpCOM’.
3. Right click the ‘AxControlsInstaller’ project and select Build.

The installer should now be located in the AxControlsInstaller’s output folder (bin\Debug or bin\Release). In the corporate domain this .msi file can de run manually on the client, or automatically with a Group Policy.

Package the installer in a .cab file for web deployment

For public web sites we obviously can’t deploy our ActiveX control to the client with a Group Policy. In this case we’re gonna have to use Internet Explores built-in ability to download and install controls that are packaged in .cab files.

1. Download the Microsoft Cabinet Software Development Kit.
2. Unpack the kit to a local folder and copy Cabarc.exe to the ‘AxControlsInstaller’ folder.
3. Create a new file named ‘AxControls.inf’ in the ‘AxControlsInstaller’ folder and add the following content:

[version]
signature="$CHICAGO$"
AdvancedINF=2.0

[Add.Code]
AxControlsInstaller.msi=AxControlsInstaller.msi

[AxControlsInstaller.msi]
file-win32-x86=thiscab
clsid={1FC0D50A-4803-4f97-94FB-2F41717F558D}
FileVersion=1,0,0,0

[Setup Hooks]
RunSetup=RunSetup

[RunSetup]
run="""msiexec.exe""" /i """%EXTRACT_DIR%\AxControlsInstaller.msi""" /qn

• Click the AxControlsInstaller project and then press F4 or (View -> Properties Window if it’s not visible).
• Click the ‘…’ button next to the PostBuildEvent property and add the following content:

"$(ProjectDir)\CABARC.EXE" N "$(ProjectDir)AxControls.cab" 
"$(ProjectDir)AxControls.inf" "$(ProjectDir)$(Configuration)\AxControlsInstaller.msi"

• Right click the ‘AxControlsInstaller’ project and select Build.
• There should now be a ‘AxControls.cab’ file in the ‘AxControlsInstaller’ folder.

Ininitalize and test the control with JavaScript

1. Right click the AxControls solution, select Add -> New Project and select ‘ASP.Net Web Application’ under ‘Web’.
2. Call the project ‘WebAppTest’ and click OK.
3. Right click the ‘WebAppTest’ project, select Add -> New Item and select ‘HTML Page’.
4. Call it ‘index.html’ and click OK.
5. Add the following content to index.html:

<html>
    <head>

        <objectname="axHello" style='display:none' id='axHello' classid='CLSID:D100C392-030A-411C-92B6-4DBE9AC7AA5A'
 codebase='AxControls.cab#version=1,0,0,0'></object>
      <script language="javascript">

        <!-- Load the ActiveX object  -->
        var x = new ActiveXObject("AxControls.HelloWorld");

        <!-- Display the String in a messagebox -->
        alert(x.GetText());

      </script>
    </head>
    <body>
    </body>
</html>
Note that 'classid' matches the GUID of the HelloWorld control.

• Right click ‘index.html’ and select ‘Set as start page’.
• Right click the ‘WebAppTest’ project and select ‘Set as startup project’.
• Copy ‘AxControls.cab’ from the ‘AxControlsInstaller’ folder to the same folder as index.html.
• Uninstall the control from the client by going to Control Panel -> Add or Remove.., selecting ‘AxControlsInstaller’ on the list and clicking Uninstall. This forces Internet Explorer to download and install the .cab file and is an important step in case you’ve already installed the control.
• Run the application (F5). This will open ‘index.html’ in Internet Explorer.
• Internet Explorer will display a security warning, asking if you want to install ‘AxControls.cab’. Click Install.

Install ActiveX

When the page loads it should display a message box with the string you defined in HelloWorld’s GetText() method.

“Hello ActiveX World!“