Folder Select Dialog

Introduction

This article describes the implementation of a simple Folder Selection dialog using C#. After designing my latest project, I found a need for a simple, easy to implement folder selection dialog for C#. The OpenFileDialog class did not suite my needs, and to integrate the COM interface to the SHBrowseForFolder, was a little more complicated that the solution I present here.

The basic dialog is built with the standard winform architecture. by modifying the window style, you can make the dialog appear as a standard windows dialog, or as a sizable window, which is the default for this example. this example was put together using Visual Studio .Net beta 2, and the IDE was used to construct the basic functionality of the UI.

Implementation

Three events are used in this dialog, OnBeforeSelect, OnBeforeExpand, and OnButtonClick. The first events are generated by the TreeView control. The OnBeforeSelect and OnBeforeExpand events both perform similar tasks. Each time the user selects a folder or clicks to expand a tree node, these events are triggered and upon receiving these events will scan the selected node identified by the Node parameter in the TreeViewCancelEventArgs class.

private void treeView1_BeforeSelect(object sender, 
                                    System.Windows.Forms.TreeViewCancelEventArgs e)
{
    getSubDirs(e.Node);                    // get the sub-folders for the selected node.
    textBox1.Text = fixPath(e.Node);        // update the user selection text box.
    folder = new DirectoryInfo(e.Node.FullPath);    // get it's Directory info.
}

private void treeView1_BeforeExpand(object sender, 
                                    System.Windows.Forms.TreeViewCancelEventArgs e)
{
    getSubDirs(e.Node);                    // get the sub-folders for the selected node.
    textBox1.Text = fixPath(e.Node);        // update the user selection text box.
    folder = new DirectoryInfo(e.Node.FullPath);    // get it's Directory info.
}

Folder select tree building

Both event handlers call a sub method called getSubDirs(). This method will scan for any sub-folders for the given folder. If this folder has been visited before, no scan is done, since it has already been entered into the tree control. Note that this does imply that if the directory structure on the hard drive your examining changes, it will not be reflected in the dialog until it has been reopened. As the user navigates to a folder, the TreeView control stores the data needed to construct a full path to the folder that the user selected. When the dialog is closed with the Select button, a DirectoryInfo variable "folder" is loaded with the DirectoryInfo information retrieved when a new instance of this class is created. The folder information is stored for later access by the application.

private void getSubDirs( TreeNode parent )
{
    DirectoryInfo directory;
    try
    {
        if ( parent.Nodes.Count == 0 )
        {
            directory = new DirectoryInfo(parent.FullPath);
            foreach( DirectoryInfo dir in directory.GetDirectories())
            {
                TreeNode newNode = new TreeNode(dir.Name);
                parent.Nodes.Add(newNode);
            }
        }

        foreach(TreeNode node in parent.Nodes)
        {
            if (node.Nodes.Count == 0)
            {
                directory = new DirectoryInfo(node.FullPath);
                foreach( DirectoryInfo dir in directory.GetDirectories())
                {
                    TreeNode newNode = new TreeNode(dir.Name);
                    node.Nodes.Add(newNode);
                }
            }
        }
    }
    catch( Exception doh )
    {
        Console.WriteLine(doh.Message);
    }
}

Folder select Properties

After closing the folder select dialog with the select button, your application can retrieve the folder information by calling the public properties fullPath, name,and info. These properties will allow for easy retrieval of any information stored within the DirectoryInfo class.

public string name
{
    get { return ((folder != null && folder.Exists))? folder.Name : null; }
}

public string fullPath
{
    get { return ((folder != null && folder.Exists && 
          treeView1.SelectedNode != null))? fixPath(treeView1.SelectedNode) : null; }
}

public DirectoryInfo info
{
    get { return ((folder != null && folder.Exists))? folder : null; }
}

Implementation details

Accessing the properties you will notice that we call a private method fixPath() to correct a problem I discovered with building the tree. The treeView will only work with paths constructed like the following example. "c:\\Program Files\Microsoft\...". What this fixPath() does is strip the leading "\\" next to the drive letter and replace it with a single "\". This should be compatible with UNC names as we expect to have a drive letter at the beginning of the string in order to correct the problem.

private string fixPath( TreeNode node )
{
    string sRet = "";
    try
    {
        sRet = node.FullPath;
        int index = sRet.IndexOf("\\\\");
        if (index > 1 )
        {
            sRet = node.FullPath.Remove(index, 1);
        }
    }
    catch( Exception doh )
    {
        Console.WriteLine(doh.Message);
    }
    return sRet;
}

Dialog invocation code

Here is an example of invoking the folder select dialog.

// invoke the folder select dialog
private void button1_Click(object sender, System.EventArgs e)
{
    try 
    {
        FolderSelect dlg = new FolderSelect();

        if ( dlg.ShowDialog() == DialogResult.OK)
        {
            DirectoryInfo info = dlg.info;
            textBox1.Text = dlg.fullPath;

            // extract the directory info.
            string [] strArray = new string[4];

            strArray[0] = "Creation Time : "+ info.CreationTime.ToString();
            strArray[1] =    "Full Name     : "+ info.FullName;
            strArray[2] = "Last Access Time : "+ info.LastAccessTime.ToString();
            strArray[3] = "Last Write Time  : "+ info.LastWriteTime.ToString();

            textBox3.Lines = strArray;
        }
    }
    catch( Exception err)
    {
        Console.WriteLine(err.Message);
    }
}

Summary

This is just a very simple Windows Form dialog. This should give you a starting point to build upon. I am not an expert on C# or Forms application at least not yet. Please do send your comments and suggestions to me. I will try to improve this application and add some more advanced features.