Create Add-In

This subroutine checks for the existence of the Add-In. The status of the
installation is reported to the user.

private void btnCheckForAddIn_Click(object sender, System.EventArgs e) 
	{
        bool isInstalled = false;
		System.Type t = System.Type.GetTypeFromProgID("VisualStudio.DTE.7.1");
		object obj = System.Activator.CreateInstance(t, true);
        // Create a DTE object, to get the Add-In informations.
        EnvDTE.DTE myDTE = (EnvDTE.DTE)obj;
        // Create a collection of all the AddIn objects.
        EnvDTE.AddIns myAddIns = myDTE.AddIns;
        // Iterate through the AddIns to determine if the C# How To
        //   Example Add-in is installed.
        foreach(EnvDTE.AddIn myAddIn in myAddIns)
		{
            if (myAddIn.Name == "How-To Example Add-In")
        {
                isInstalled = true;
            }
        }
        // Report installation status to the user.
		if (isInstalled) 
		{
		txtInstalled.Text = "C# How To Example Add-in is installed!";
		}
		else 
		{
		txtInstalled.Text = "C# How To Example Add-in is not installed!";
		}
    }

private void frmMain_Load(object sender, System.EventArgs e) 
{
  Call the btnCheckForAddIn_Click subroutine.
  btnCheckForAddIn_Click(this, new System.EventArgs());
}