Introduction

In this tip, I provide you with a CustomFolderBrowserDialog which allows you to limit browsing directories to a non-special folder.

Background

A much desired feature which is locked in .NET native FolderBrowserDiaog is the capability to set RootFolder to some custom folder. Some applications need to limit the user to browse only the sub directories of a specified folder, not the whole hard drives.

The ShowCFBD Method

The CustomFolderBrowserDialog is presented as a simple method call, you just need to pass your desired parameters to this method and it will show your directory hierarchy with your desired root folder not limited to Environment.SpecialFolder enum.

ShowCFBD has the following arguments and return value:

rootFolder: a string representing the path of your desired RootFolder
title: The description title appears on top of dialog
selectedPath: which is filled by the path the user selects
returns boolean: The return value specifies if the user has pressed OK or Cancel button

public bool ShowCFBD(String rootFolder, String title, out String selectedPath)
{
    var shellType = Type.GetTypeFromProgID("Shell.Application");

    var shell = Activator.CreateInstance(shellType);

    var result = shellType.InvokeMember
    ("BrowseForFolder", BindingFlags.InvokeMethod, null, shell, new object[] 
    { 0, title, 0, rootFolder });

    if (result == null)
    {
        selectedPath = "";

        return false;
    }
    else
    {
        StringBuilder sb = new StringBuilder();

        while (result != null)
        {
            var folderName = result.GetType().InvokeMember("Title", BindingFlags.GetProperty,
                null, result, null).ToString();

            sb.Insert(0, String.Format(@"{0}\", folderName));

            result = result.GetType().InvokeMember("ParentFolder", BindingFlags.GetProperty,
                null, result, null);
        }

        selectedPath = sb.ToString();

        selectedPath = Regex.Replace(selectedPath, @"Desktop\\Computer\\.*\(\w:\)\\",
            rootFolder.Substring(0, 3));

        return true;
    }
}

Using the Code

The code usage is very simple, just call the ShowCFBD method passing an out string path to that and checking the return boolean value.

     String selectedPath;
	
    if (ShowCFBD(@"C:\", "Please select a folder", out selectedPath)) 
    {
        MessageBox.Show("You've selected the " + selectedPath);
    } 
    else
    {
        MessageBox.Show("Please select a folder first");
    }