Launch associated program or show “Open with” dialog from another program

Question

Under Window Seven, the following command displays a dialog box then terminates without any other action, why?

The expected effect is launching the associated progra

Answer 1

Based on other answers to similar questions and on code from CodeProject: Calling the Open With dialog box from your application, using C# and PInvoke.net: SHOpenWithDialog (shell32) this is the code which works for me

ShellHelper.OpenAs(mainForm.Handle, "path/to/file")

both on Windows XP and on Windows Vista and later. This code uses only documented API (no rundll32)

public class ShellHelper
{
    #region http://www.pinvoke.net/default.aspx/shell32/SHOpenWithDialog.html

    [DllImport("shell32.dll", EntryPoint = "SHOpenWithDialog", CharSet = CharSet.Unicode)]
    private static extern int SHOpenWithDialog(IntPtr hWndParent, ref tagOPENASINFO oOAI);

    // http://msdn.microsoft.com/en-us/library/windows/desktop/bb773363(v=vs.85).aspx 
    private struct tagOPENASINFO
    {
        [MarshalAs(UnmanagedType.LPWStr)]
        public string cszFile;

        [MarshalAs(UnmanagedType.LPWStr)]
        public string cszClass;

        [MarshalAs(UnmanagedType.I4)]
        public tagOPEN_AS_INFO_FLAGS oaifInFlags;
    }

    [Flags]
    private enum tagOPEN_AS_INFO_FLAGS
    {
        OAIF_ALLOW_REGISTRATION = 0x00000001,   // Show "Always" checkbox
        OAIF_REGISTER_EXT = 0x00000002,   // Perform registration when user hits OK
        OAIF_EXEC = 0x00000004,   // Exec file after registering
        OAIF_FORCE_REGISTRATION = 0x00000008,   // Force the checkbox to be registration
        OAIF_HIDE_REGISTRATION = 0x00000020,   // Vista+: Hide the "always use this file" checkbox
        OAIF_URL_PROTOCOL = 0x00000040,   // Vista+: cszFile is actually a URI scheme; show handlers for that scheme
        OAIF_FILE_IS_URI = 0x00000080    // Win8+: The location pointed to by the pcszFile parameter is given as a URI
    }

    private static void DoOpenFileWith(IntPtr hwndParent, string sFilename)
    {
        tagOPENASINFO oOAI = new tagOPENASINFO();
        oOAI.cszFile = sFilename;
        oOAI.cszClass = String.Empty;
        oOAI.oaifInFlags = tagOPEN_AS_INFO_FLAGS.OAIF_ALLOW_REGISTRATION | tagOPEN_AS_INFO_FLAGS.OAIF_EXEC;
        SHOpenWithDialog(hwndParent, ref oOAI);
    }

    #endregion

    #region http://www.codeproject.com/Articles/13103/Calling-the-Open-With-dialog-box-from-your-applica

    [Serializable]
    private struct ShellExecuteInfo
    {
        public int Size;
        public uint Mask;
        public IntPtr hwnd;
        public string Verb;
        public string File;
        public string Parameters;
        public string Directory;
        public uint Show;
        public IntPtr InstApp;
        public IntPtr IDList;
        public string Class;
        public IntPtr hkeyClass;
        public uint HotKey;
        public IntPtr Icon;
        public IntPtr Monitor;
    }

    // Code For OpenWithDialog Box

    [DllImport("shell32.dll", SetLastError = true)]
    extern private static bool ShellExecuteEx(ref ShellExecuteInfo lpExecInfo);

    private const uint SW_NORMAL = 1;

    private static void OpenAsOld(IntPtr hwndParent, string file)
    {
        ShellExecuteInfo sei = new ShellExecuteInfo();
        sei.Size = Marshal.SizeOf(sei);
        sei.Verb = "openas";
        sei.File = file;
        sei.Show = SW_NORMAL;
        sei.hwnd = hwndParent;
        if (!ShellExecuteEx(ref sei))
            throw new System.ComponentModel.Win32Exception();
    }

    #endregion

    public static void OpenAs(IntPtr hWndParent, string file)
    {
        if (System.Environment.OSVersion.Version.Major > 5)
        {
            DoOpenFileWith(hWndParent, file);
        }
        else
        {
            OpenAsOld(hWndParent, file);
        }
    }
}