I'm developing a proof of concept web application: A web page with a button that opens the Word Application installed on the user's PC.

I'm stuck with a C# project in Visual Studio 2008 Express (Windows XP client, LAMP server). I've followed the Writing an ActiveX Control in .NET tutorial and after some tuning it worked fine. Then I added my button for opening Word.

The problem is that I can reference the Microsoft.Office.Interop.Word from the project, but I'm not able to access it from the web page. The error says "That assembly does not allow partially trusted callers".

I've read a lot about security in .NET, but I'm totally lost now. Disclaimer: I'm into .NET since 4 days ago.

I've tried to work around this issue but I cannot see the light!! I don't even know if it will ever be possible!

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using Word = Microsoft.Office.Interop.Word;

using System.IO;
using System.Security.Permissions;

using System.Security;
[assembly: AllowPartiallyTrustedCallers]

namespace OfficeAutomation
{
    public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();
        }

        private void openWord_Click(object sender, EventArgs e)
        {
            try
            {
                Word.Application Word_App = null;
                Word_App = new Word.Application();
                Word_App.Visible = true;
            }
            catch (Exception exc)
            {
                MessageBox.Show("Can't open Word application (" + exc.ToString() + ")");
            }
        }
    }
}