Automated IE SaveAs MHTML

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;

using SHDocVw;

namespace De.Fun.IESaveAsHack
{
  /// <summary>
  /// IE has this file options in the "SaveAs" dialog
  /// </summary>
  public enum SaveType
  {
    SAVETYPE_HTMLPAGE = 0,
    SAVETYPE_ARCHIVE,
    SAVETYPE_HTMLONLY,
    SAVETYPE_TXTONLY
  };

  /// <summary>
  /// Because security reasons the IE always shows a "Save As" dialog box if you want to save a html page complete.
  /// This helper class automatically fills out the fields and presses ok.
  /// </summary>
  public class SaveAsWebbrowser  
  {
    /// <summary>
    /// Construction
    /// </summary>
    /// <param name="webbrowser">Webbrowser interface</param>
    /// <param name="pathFile">Path and filename</param>
    /// <param name="saveType">Type of file</param>
    public SaveAsWebbrowser(IWebBrowser2 webbrowser, string pathFile, SaveType saveType)
    {
      this.WebBrowser = webbrowser;
      this.PathFile = pathFile;
      this.SaveType = saveType;
    }

    IWebBrowser2 webBrowser;
    public IWebBrowser2 WebBrowser
    {
      get { return webBrowser; }
      set { webBrowser = value; }
    }

    string pathFile;
    public string PathFile
    {
      get { return pathFile; }
      set { pathFile = value; }
    }

    SaveType saveType;
    public SaveType SaveType
    {
      get { return saveType; }
      set { saveType = value; }
    }

    /// <summary>
    /// Call this function to save current page - after page is loaded complete
    /// </summary>
    /// <returns>true if successful</returns>
    public bool SaveAs()
    {
      if (0==pathFile.Length)
        pathFile = "untitled";
      // TODO check path file. If file exists, IE prompts again...

      if (null==webBrowser)
        return false;
      
      if (0!=hook)
        return false;

      HookProcedure = new HookProc(SaveAsHookProc);

      // prepare SaveAs dialog hook
      hook = SetWindowsHookEx(5 /*WH_CBT*/, HookProcedure, (IntPtr) 0, AppDomain.GetCurrentThreadId());
      if (0==hook)
        return false;

      // this will show the dialog
      saveaswebbrowser = this;
      object o = null;
      webBrowser.ExecWB(SHDocVw.OLECMDID.OLECMDID_SAVEAS,
        SHDocVw.OLECMDEXECOPT.OLECMDEXECOPT_PROMPTUSER, ref o, ref o);

      // remove hook
      UnhookWindowsHookEx(hook);
      saveaswebbrowser = null;
      hook = 0;
      return true;
    }

    //Import for SetWindowsHookEx.
    [DllImport("user32.dll",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
    public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

    //Import for UnhookWindowsHookEx.
    [DllImport("user32.dll",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
    public static extern bool UnhookWindowsHookEx(int idHook);

    //Import for CallNextHookEx.
    //Use this function to pass the hook information to next hook procedure in chain.
    [DllImport("user32.dll",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
    public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);

    // Hook variables
    public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);
    static int hook = 0;
    HookProc HookProcedure;        

    static IntPtr hwndDlg = (IntPtr) 0;
    static SaveAsWebbrowser saveaswebbrowser = null;

    [StructLayout(LayoutKind.Sequential)]
    public struct CBT_CREATEWND 
    { 
      public IntPtr   lpcs; 
      int             hwndInsertAfter; 
    }; 

    [StructLayout(LayoutKind.Sequential)]
    public struct CREATESTRUCT 
    {
      int             lpCreateParams;
      int             hInstance;
      int             hMenu;
      int             hwndParent;
      int             cy;
      public int      cx;
      int             y;
      public int      x;
      int             style;
      int             lpszName;
      public int      lpszClass;
      int             dwExStyle;
    } 

    /// <summary>
    /// The hook procedure for dialogs. Only called by windows.
    /// </summary>
    /// <param name="nCode">Action code</param>
    /// <param name="wParam">Depends on action code</param>
    /// <param name="lParam">Depends on action code</param>
    /// <returns></returns>
    public static int SaveAsHookProc(int nCode, IntPtr wParam, IntPtr lParam)
    {
      switch(nCode)
      {
        case 3:  // HCBT_CREATEWND
          CBT_CREATEWND cw = (CBT_CREATEWND) Marshal.PtrToStructure(lParam, typeof(CBT_CREATEWND));
          CREATESTRUCT cs = (CREATESTRUCT) Marshal.PtrToStructure(cw.lpcs, typeof(CREATESTRUCT));
          if (cs.lpszClass == 0x00008002 && (IntPtr)0 == hwndDlg)
          {
            hwndDlg = (IntPtr) wParam;  // Get hwnd of SaveAs dialog
            cs.x = -2 * cs.cx;          // Move dialog off screen
          }
          break;
        case 5: // HCBT_ACTIVATE
          ThreadPressOk tpok = new ThreadPressOk(hwndDlg, saveaswebbrowser.PathFile, saveaswebbrowser.SaveType);
          hwndDlg = (IntPtr) 0;
          // Create a thread to execute the task, and then
          // start the thread.
          new Thread((new ThreadStart(tpok.ThreadProc))).Start();
          break;
      }
      return CallNextHookEx(hook, nCode, wParam, lParam); 
    }

    /// <summary>
    /// Helper thread class.
    /// </summary>
    class ThreadPressOk 
    {
      public ThreadPressOk(IntPtr hwndDlg, string pathFile, SaveType saveType)
      {
        this.hwndDlg = hwndDlg;
        this.pathFile = pathFile;
        this.saveType = saveType;
      }
      
      IntPtr    hwndDlg;
      string    pathFile;
      SaveType  saveType;

      // Imports of the User32 DLL.   
      [DllImport("user32.dll", CharSet=CharSet.Auto)]
      public static extern IntPtr SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);

      [DllImport("user32.dll", CharSet=CharSet.Auto)]
      public static extern IntPtr GetDlgItem(IntPtr hWnd, int nIDDlgItem);

      [DllImport("user32.dll", CharSet=CharSet.Auto)]
      static extern private bool SetWindowText(IntPtr hWnd, string lpString);
         
      // The thread procedure performs the message loop and place the data
      public void ThreadProc() 
      {        
        // Create the dialog
        Application.DoEvents();
    
        //  Begin saving the webpage
        //  Note: these settings only work on win2k IE 6 SP1
        //  You can make them work the same way on other versions

        // editbox : filepath (control id = 0x047c)
        // dropdown combo : filetypes (options=complete page|archive|html only|txt) (control id = 0x0470)
        // save button : control id = 0x0001
        // cancel button : control id = 0x0002

        IntPtr typeB = GetDlgItem(hwndDlg, 0x0470);
        IntPtr nameB = GetDlgItem(hwndDlg, 0x047c);
        IntPtr saveBtn = GetDlgItem(hwndDlg, 0x0001);
        if (((IntPtr)0!=typeB) && ((IntPtr)0!=nameB) && ((IntPtr)0!=saveBtn))
        {
          //select save type
          SendMessage(typeB, 0x014E /*CB_SETCURSEL*/, (int)saveType, 0);
          SendMessage(hwndDlg, 0x0111 /*WM_COMMAND*/, 0x80470/*MAKEWPARAM(0x0470, CBN_CLOSEUP)*/, (int)typeB);
          // set output pathFile
          SetWindowText(nameB, pathFile);
          // Invoke Save button
          SendMessage(saveBtn, 0x00F5 /*BM_CLICK*/, 0, 0);
        }
        // Clean up GUI - we have clicked ok
        Application.DoEvents();

        // thread finish, garbage collection should do the clean up...
      }
    }
  }
}