Trying to open a file dialog using the new IFileDialog and IFileOpenDialog interfaces in C# with minimal code

Question

I'm trying to display a standard open file dialog that can select folders, using the IFileOpenDialog interface in C#, Visual Studio 2010.

I'm trying to use the minimal code, so I've only defined the methods I need in the interfaces:

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

// Disable warning CS0108: 'x' hides inherited member 'y'. Use the new keyword if hiding was intended.
\#pragma warning disable 0108

namespace FolderDialog
{

internal static class IIDGuid
{
    internal const string IModalWindow = "b4db1657-70d7-485e-8e3e-6fcb5a5c1802";
    internal const string IFileDialog = "42f85136-db7e-439c-85f1-e4075d135fc8";
    internal const string IFileOpenDialog = "d57c7288-d4ad-4768-be02-9d969532d960";
}

internal static class CLSIDGuid
{
    internal const string FileOpenDialog = "DC1C5A9C-E88A-4dde-A5A1-60F82A20AEF7";
}

static class NativeMethods
{

    [Flags]
    internal enum FOS : uint
    {
        FOS_PICKFOLDERS = 0x00000020
    }

}

[ComImport(),
Guid(IIDGuid.IModalWindow),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface IModalWindow
{

    [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime),
    PreserveSig]
    int Show([In] IntPtr parent);
}

[ComImport(),
Guid(IIDGuid.IFileDialog),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface IFileDialog : IModalWindow
{
    // Defined on IModalWindow - repeated here due to requirements of COM interop layer
    // --------------------------------------------------------------------------------
    [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime),
    PreserveSig]
    int Show([In] IntPtr parent);

    [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
    void SetOptions([In] NativeMethods.FOS fos);
}

[ComImport(),
Guid(IIDGuid.IFileOpenDialog),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
internal interface IFileOpenDialog : IFileDialog
{
    // Defined on IModalWindow - repeated here due to requirements of COM interop layer
    // --------------------------------------------------------------------------------
    [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime),
    PreserveSig]
    int Show([In] IntPtr parent);

    [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
    void SetOptions([In] NativeMethods.FOS fos);
}


// ---------------------------------------------------
// .NET classes representing runtime callable wrappers
[ComImport,
ClassInterface(ClassInterfaceType.None),
TypeLibType(TypeLibTypeFlags.FCanCreate),
Guid(CLSIDGuid.FileOpenDialog)]
internal class FileOpenDialogRCW
{
}

// ---------------------------------------------------------
// Coclass interfaces - designed to "look like" the object 
// in the API, so that the 'new' operator can be used in a 
// straightforward way. Behind the scenes, the C# compiler
// morphs all 'new CoClass()' calls to 'new CoClassWrapper()'
[ComImport,
Guid(IIDGuid.IFileOpenDialog),
CoClass(typeof(FileOpenDialogRCW))]
internal interface NativeFileOpenDialog : IFileOpenDialog
{
}

}

If I only call

        IFileDialog dialog = null;
        try
        {
            dialog = new NativeFileOpenDialog();
            dialog.Show(IntPtr.Zero);
        }
        finally
        {
            if (dialog != null)
                System.Runtime.InteropServices.Marshal.FinalReleaseComObject(dialog);
        }

it works fine and it opens the File Dialog without any errors.

If I try:

        IFileDialog dialog = null;
        try
        {
            dialog = new NativeFileOpenDialog();
            dialog.SetOptions(NativeMethods.FOS.FOS_PICKFOLDERS);
            dialog.Show(IntPtr.Zero);
        }
        finally
        {
            if (dialog != null)
                System.Runtime.InteropServices.Marshal.FinalReleaseComObject(dialog);
        }

so If I add a call to the SetOptions method before the Show method call, I get an exception: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt."

I get this trying to run on .Net 2.0 or even 4.0.

What is the error here? Why does just calling the Show method work, but if I try another method before it fails?

Why are you using the native method instead of the managed version? — Scott Chamberlain, Nov 09 '10 at 19:43
I want to be able to open folders, not files, the managed version can only open files. — TechAurelian, Nov 11 '10 at 11:32

score 5 · Accepted Answer · edited May 23 '17 at 12:02

Here's a class that opens a Vista-style folder picker using the .Net private IFileDialog interface, without directly using interop in the code (.Net takes care of that for you). It falls back to the pre-Vista dialog if not in a high enough Windows version. Should work in Windows 7, 8, 9, 10 and higher (theoretically).

using System;
using System.Reflection;
using System.Windows.Forms;

namespace Ris.Shuriken {
    /// <summary>
    /// Present the Windows Vista-style open file dialog to select a folder. Fall back for older Windows Versions
    /// </summary>
    public class FolderSelectDialog {
        private string _initialDirectory;
        private string _title;
        private string _fileName = "";

        public string InitialDirectory {
            get { return string.IsNullOrEmpty(_initialDirectory) ? Environment.CurrentDirectory : _initialDirectory; }
            set { _initialDirectory = value; }
        }
        public string Title {
            get { return _title ?? "Select a folder"; }
            set { _title = value; }
        }
        public string FileName { get { return _fileName; } }

        public bool Show() { return Show(IntPtr.Zero); }

        /// <param name="hWndOwner">Handle of the control or window to be the parent of the file dialog</param>
        /// <returns>true if the user clicks OK</returns>
        public bool Show(IntPtr hWndOwner) {
            var result = Environment.OSVersion.Version.Major >= 6
                ? VistaDialog.Show(hWndOwner, InitialDirectory, Title)
                : ShowXpDialog(hWndOwner, InitialDirectory, Title);
            _fileName = result.FileName;
            return result.Result;
        }

        private struct ShowDialogResult {
            public bool Result { get; set; }
            public string FileName { get; set; }
        }

        private static ShowDialogResult ShowXpDialog(IntPtr ownerHandle, string initialDirectory, string title) {
            var folderBrowserDialog = new FolderBrowserDialog {
                Description = title,
                SelectedPath = initialDirectory,
                ShowNewFolderButton = false
            };
            var dialogResult = new ShowDialogResult();
            if (folderBrowserDialog.ShowDialog(new WindowWrapper(ownerHandle)) == DialogResult.OK) {
                dialogResult.Result = true;
                dialogResult.FileName = folderBrowserDialog.SelectedPath;
            }
            return dialogResult;
        }

        private static class VistaDialog {
            private const string c_foldersFilter = "Folders|\n";

            private const BindingFlags c_flags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
            private readonly static Assembly s_windowsFormsAssembly = typeof(FileDialog).Assembly;
            private readonly static Type s_iFileDialogType = s_windowsFormsAssembly.GetType("System.Windows.Forms.FileDialogNative+IFileDialog");
            private readonly static MethodInfo s_createVistaDialogMethodInfo = typeof(OpenFileDialog).GetMethod("CreateVistaDialog", c_flags);
            private readonly static MethodInfo s_onBeforeVistaDialogMethodInfo = typeof(OpenFileDialog).GetMethod("OnBeforeVistaDialog", c_flags);
            private readonly static MethodInfo s_getOptionsMethodInfo = typeof(FileDialog).GetMethod("GetOptions", c_flags);
            private readonly static MethodInfo s_setOptionsMethodInfo = s_iFileDialogType.GetMethod("SetOptions", c_flags);
            private readonly static uint s_fosPickFoldersBitFlag = (uint) s_windowsFormsAssembly
                .GetType("System.Windows.Forms.FileDialogNative+FOS")
                .GetField("FOS_PICKFOLDERS")
                .GetValue(null);
            private readonly static ConstructorInfo s_vistaDialogEventsConstructorInfo = s_windowsFormsAssembly
                .GetType("System.Windows.Forms.FileDialog+VistaDialogEvents")
                .GetConstructor(c_flags, null, new[] { typeof(FileDialog) }, null);
            private readonly static MethodInfo s_adviseMethodInfo = s_iFileDialogType.GetMethod("Advise");
            private readonly static MethodInfo s_unAdviseMethodInfo = s_iFileDialogType.GetMethod("Unadvise");
            private readonly static MethodInfo s_showMethodInfo = s_iFileDialogType.GetMethod("Show");

            public static ShowDialogResult Show(IntPtr ownerHandle, string initialDirectory, string title) {
                var openFileDialog = new OpenFileDialog {
                    AddExtension = false,
                    CheckFileExists = false,
                    DereferenceLinks = true,
                    Filter = c_foldersFilter,
                    InitialDirectory = initialDirectory,
                    Multiselect = false,
                    Title = title
                };

                var iFileDialog = s_createVistaDialogMethodInfo.Invoke(openFileDialog, new object[] { });
                s_onBeforeVistaDialogMethodInfo.Invoke(openFileDialog, new[] { iFileDialog });
                s_setOptionsMethodInfo.Invoke(iFileDialog, new object[] { (uint) s_getOptionsMethodInfo.Invoke(openFileDialog, new object[] { }) | s_fosPickFoldersBitFlag });
                var adviseParametersWithOutputConnectionToken = new[] { s_vistaDialogEventsConstructorInfo.Invoke(new object[] { openFileDialog }), 0U };
                s_adviseMethodInfo.Invoke(iFileDialog, adviseParametersWithOutputConnectionToken);

                try {
                    int retVal = (int) s_showMethodInfo.Invoke(iFileDialog, new object[] { ownerHandle });
                    return new ShowDialogResult {
                        Result = retVal == 0,
                        FileName = openFileDialog.FileName
                    };
                }
                finally {
                    s_unAdviseMethodInfo.Invoke(iFileDialog, new[] { adviseParametersWithOutputConnectionToken[1] });
                }
            }
        }

        // Wrap an IWin32Window around an IntPtr
        private class WindowWrapper : IWin32Window {
            private readonly IntPtr _handle;
            public WindowWrapper(IntPtr handle) { _handle = handle; }
            public IntPtr Handle { get { return _handle; } }
        }
    }
}

I developed this as a cleaned up version of .NET Win 7-style folder select dialog by Bill Seddon of lyquidity.com (I have no affiliation). I wrote my own because his solution requires an additional Reflection class that isn't needed for this focused purpose, uses exception-based flow control, doesn't cache the results of its reflection calls. Note that the nested static VistaDialog class is so that its static reflection variables don't try to get populated if the Show method is never called.

It is used like so in a Windows Form:

var dialog = new FolderSelectDialog {
    InitialDirectory = musicFolderTextBox.Text
    Title = "Select a folder to import music from"
};
if (dialog.Show(Handle)) {
    musicFolderTextBox.Text = dialog.FileName;
}

You can of course play around with its options and what properties it exposes. For example, it allows multiselect in the Vista-style dialog.

As alluded to in his answer in this thread, Simon Mourier's answer on another question shows how to do the job using interop directly. Unfortunately, I hadn't found that yet when I worked up my solution. Name your poison!

Is there any way (eg some flag) to enable the user to choose a Folder OR File at the same time? Alternatively: Is there any way to show also the files inside each folder when user browse to select a folder? — S.Serpooshan, Jul 22 '19 at 10:15

score 5 · Answer 2 · edited Jul 20 '11 at 22:15

5

The Windows® API Code Pack for Microsoft® .NET Framework can help. After you download it, look at "\Windows API Code Pack 1.1\source\WindowsAPICodePack\Shell\CommonFileDialogs\CommonFileDialog.cs" to see how it uses IFileDialogCustomize from COM.

Hope this helps.

edited Jul 20 '11 at 22:15

Kate Gregory

18,808
8
56
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answered Jul 20 '11 at 08:17

capcom923

638
5
15

1

The above link to the API Code Pack is broken, but see [this SO question](http://stackoverflow.com/questions/24081665/windows-api-code-pack-where-is-it). – Oliver Bock Jul 28 '16 at 04:57

score 2 · Answer 3 · edited May 23 '17 at 11:46

2

A bit late, but you can find an example of IFileDialog interfaces in C# here on SO in my answer: Show detailed Folder Browser from a PropertyGrid and another variation that allows the selection of non file system folders (like My Computer/This PC) here: C# How to allow selection of My Computer with folderBrowserDialog

edited May 23 '17 at 11:46

Community

1
1

answered Mar 13 '13 at 13:49

Simon Mourier

132,049
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298

See my [new answer referencing yours](http://stackoverflow.com/a/33835934/57611). I think this answer would be vastly improved if you just copied and pasted your entire answer that you linked. – ErikE Nov 20 '15 at 20:57
@ErikE - well, thanks for pinging me, but I now have two related answers so I'm kinda torn between the variations :-) – Simon Mourier Nov 21 '15 at 08:08

score 1 · Answer 4 · answered Jun 03 '11 at 15:00

1

If you're simply trying to open a folder browser dialog, you may be over-complicating the issue. Use the FolderBrowserDialog class instead.

answered Jun 03 '11 at 15:00

Special Touch

476
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7

The problem with `FolderBrowserDialog` is that it doesn't let you type in a textbox (or copy or paste) and it doesn't show favorites and sometimes certain network locations. It can be really hard to work with. It also doesn't allow multi-select. – ErikE Nov 20 '15 at 20:02

Trying to open a file dialog using the new IFileDialog and IFileOpenDialog interfaces in C# with minimal code

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