ActiveX control's constructor invokes second time

Question

I have a couple of questions here related to IIS and ActiveX controls.

I am developing an activeX control by this tutorial http://haseebakhtar.wordpress.com/2011/05/31/creating-an-activex-control-in-net-using-c/. I am using IE9 for its testing and VS 2010 as IDE. Here is the code:

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


namespace AxControls
{
    [ComVisible(true)]
    [ClassInterface(ClassInterfaceType.None)]
    [Guid("42BBA00A-515E-45b5-9EAF-3827F7AEB4FA")]
    [ProgId("AxControls.HelloWorld")]
    [ComDefaultInterface(typeof(IClip))]
    public class HelloWorld : UserControl, IObjectSafety, IClip
    {
        public HelloWorld()
        {
            MessageBox.Show("Starting");
        }

        [STAThread]
        public Image GetClipboardImage()
        {
            MessageBox.Show("try to get image");
            Image returnImage = null;
            if (Clipboard.ContainsImage())
            {
                MessageBox.Show("getting image");
                returnImage = Clipboard.GetImage();
            }
            return returnImage;
        }

        private void SaveImage(Image image)
        {
            try
            {
                if (image != null)
                {
                    MessageBox.Show("saving image");
                    image.Save("C:\\test.jpg");
                }
            }
            catch (Exception e)
            {
                MessageBox.Show(e.StackTrace);
            }
        }

        public void SaveImgFromClipBoard()
        {
            Image img = GetClipboardImage();
            SaveImage(img);
        }

        #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
    }
}

Here is another code:

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

namespace AxControls
{
    [ComImport()]
    [Guid("5DC2DE9B-8D7D-490e-A904-C8CBFFD38412")]
    [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);
    }
}

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

namespace AxControls
{
    [ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    [Guid("013BFB31-B3F8-4bae-B5C2-5F6D22B815E3")]
    public interface IClip
    {
        void SaveImgFromClipBoard();
    }
}

and that is how I call it:

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

namespace AxControls
{
    [ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    [Guid("013BFB31-B3F8-4bae-B5C2-5F6D22B815E3")]
    public interface IClip
    {
        void SaveImgFromClipBoard();
    }
}

1) So, when I am refreshing the page I see two message boxes with "Starting" and they appear one by another. I fail to see why. I run it in debug mode (using IIS of course + ASP.NET web project + HTML file inside it). That is my post build action

"C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools\x86\gacutil.exe" /f /i "$(TargetDir)$(TargetFileName)"
"C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools\x64\gacutil.exe" /f /i "$(TargetDir)$(TargetFileName)"

"C:\Windows\Microsoft.NET\Framework\v4.0.30319\RegAsm.exe" /unregister "$(TargetDir)$(TargetFileName)"
"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe" /unregister "$(TargetDir)$(TargetFileName)"

"C:\Windows\Microsoft.NET\Framework\v4.0.30319\RegAsm.exe" "$(TargetDir)$(TargetFileName)"
"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe" "$(TargetDir)$(TargetFileName)"

I even tried to use it on Apache Web Server - but had the same situation - constructor seems to invokes twice.

2) Many times when I am changing my HTML file in Visual Studio and run it in debug mode the changes is not visible in my Browser. I tried to clean IE history and cache with no success. Looks like IIS puts it in cache. Can it be? How can I avoid it?

3) I cannot understand the purpose of adding all that IObjectSafety Members.

UPDATE:

<html>
    <head>

        <object name="axHello" style='display:none' id='axHello' classid='CLSID:42BBA00A-515E-45b5-9EAF-3827F7AEB4FA'
 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 ffff-->
        x.SaveImgFromClipBoard();
      </script>
    </head>
    <body>
    </body>
</html>

Answer 1

Now that we've seen your HTML code, it's clear: you create two separate objects: one as object tag, another one - dynamically - as new ActiveXObject("AxControls.HelloWorld"). Remove the the second one, and just call:

axHello.SaveImgFromClipBoard();

Don't forget about my notes on IObjectSafety in the comments. The best thing to do is to lock your control to your own site(s).

Regarding this: 2) Many times when I am changing my HTML file in Visual Studio and run it in debug mode the changes is not visible in my Browser. I tried to clean IE history and cache with no success. Looks like IIS puts it in cache. Can it be? How can I avoid it?

When it happens next time, close all IE windows, then use Process Explorer to check if there is a hidden iexplore.exe process still hanging in. If so, kill it (all instances), then clear the cache. The next time it should load a fresh version of your page.

If that happens, it's actually a bad sign that your control doesn't shutdown properly (but that would be a subject for a separate question).