Caution: Incorrectly editing the registry may severely damage your system. Back up the current version of the registry before making any changes. You should also back up any valued data on the computer.

I found various ways to do it, but the easy way I found I am sharing.

Dim SDF As RegistryKey = My.Computer.Registry.ClassesRoot. _
    CreateSubKey(".sdx")
SDF.SetValue("", "SDFUtility", RegistryValueKind.String)
Dim OpenCommand As RegistryKey =
    My.Computer.Registry.ClassesRoot.CreateSubKey _
    ("SDFUtility\Shell\Explore with SDFUtility\Command")
OpenCommand.SetValue("", String.Format("{0} ""%1""", appPath), _
                        Microsoft.Win32.RegistryValueKind.String)

And here is the screenshot

Default menu item after associating the File with application

You can remove the association by reseting the sdf key’s value. And you can delete all the keys by calling a DeleteSubKeyTree method on the SDFUtility key to remove all the keys associated with it.

SDF = My.Computer.Registry.ClassesRoot.OpenSubKey(".sdf", True)
SDF.SetValue("", "Microsoft SQL Server Compact Edition Database File", _
                     RegistryValueKind.String)
My.Computer.Registry.ClassesRoot.DeleteSubKeyTree("SDFUtility")

You need be Administrator do this operation, otherwise you may get an exception in Windows Vista+.

Open File Dialog in Visual Studio

We can also implement the same functionality in our applications by using CustomPlaces collection property of FileDialog class. The OpenFileDialog and SaveFileDialog classes allow you to add folders to the CustomPlaces collection.

openFileDialog.CustomPlaces.Add(@"C:\Users");

You can also specify GUID of Windows Vista known folder. Known Folder GUIDs are not case sensitive and are defined in the KnownFolders.h file in the Windows SDK. If the specified Known Folder is not present on the computer that is running the application, the Known Folder is not shown.

openFileDialog.CustomPlaces.Add(@"C:\Users");
//Desktop Folder
openFileDialog.CustomPlaces.Add(new Guid("B4BFCC3A-DB2C-424C-B029-7FE99A87C641"));
//Downloads Folder
openFileDialog.CustomPlaces.Add(new Guid("374DE290-123F-4565-9164-39C4925E467B"));

Open File Dialog with Custom Places

Note: This feature will not have any effect in Windows XP. Also you must set the AutoUpgradeEnabled to True(default) to enable this feature in Vista or Windows 7.

The following table lists few Windows Vista Known Folders and their associated Guid.

1. Contacts : 56784854-C6CB-462B-8169-88E350ACB882
2. ControlPanel : 82A74AEB-AEB4-465C-A014-D097EE346D63
3. Desktop : B4BFCC3A-DB2C-424C-B029-7FE99A87C641
4. Documents : FDD39AD0-238F-46AF-ADB4-6C85480369C7
5. Downloads : 374DE290-123F-4565-9164-39C4925E467B
6. Favorites : 1777F761-68AD-4D8A-87BD-30B759FA33DD
7. Fonts : FD228CB7-AE11-4AE3-864C-16F3910AB8FE
8. Music : 4BD8D571-6D19-48D3-BE97-422220080E43

I created a Windows Application Project and Added reference of the following libraries

atk-sharp.dll
gdk-sharp.dll
glade-sharp.dll
glib-sharp.dll
gtk-dotnet.dll
gtk-sharp.dll

And I deleted the Form1. And modified the Program.cs; the Program.cs

namespace HelloGtk
{
    using System;
    using Gtk;

    public class Program
    {
        private MainWindow mainWindow = null;

        public Program()
        {
            Application.Init();
            mainWindow = new MainWindow();
            Application.Run();
        }

        static void Main()
        {
            new Program();
            return;
        }
    }
}

And the added a class MainWindow.cs, and wrote the code

namespace HelloGtk
{
    using Gtk;
    using System.IO;

    public class MainWindow : Gtk.Window
    {
        private string title = "Text File Viewer";
        private VBox vbox;
        private MenuBar menubar;
        private Statusbar statusbar;
        private TextView textView;
        private ScrolledWindow scrolledWindow;
        private AccelGroup accelGroup;
        private Toolbar toolbar;
        public MainWindow()
            : base("Text File Viewer")
        {
            this.DefaultSize = new Gdk.Size(600, 500);
            this.DeleteEvent += new DeleteEventHandler(MainWindow_DeleteEvent);
            this.Build();
        }

        private void MainWindow_DeleteEvent(object o, DeleteEventArgs args)
        {
            Application.Quit();
            args.RetVal = true;
        }

        private void Build()
        {
            this.Title = this.title;
            this.vbox = new VBox(false, 0);
            this.CreateMenubar();
            this.vbox.PackStart(this.menubar, false, true, 0);
            this.toolbar = new Toolbar();
            this.CreateToolbar();
            this.vbox.PackStart(this.toolbar, false, true, 0);
            this.textView = new TextView();
            this.textView.Editable = false;
            this.textView.WrapMode = WrapMode.Word;
            this.scrolledWindow = new ScrolledWindow();
            this.scrolledWindow.SetPolicy(PolicyType.Automatic, PolicyType.Automatic);
            this.scrolledWindow.Add(this.textView);
            this.vbox.PackStart(this.scrolledWindow, true, true, 0);
            this.statusbar = new Statusbar();
            this.vbox.PackStart(this.statusbar, false, true, 0);
            this.Add(this.vbox);
            this.ShowAll();
        }
        private void CreateToolbar()
        {
            ToolButton OpenToolBarBtn = new ToolButton("gtk-open");
            OpenToolBarBtn.Clicked += this.openMenu_Activated;
            SeparatorToolItem Sep1 = new SeparatorToolItem();
            ToolButton CopyToolBarBtn = new ToolButton("gtk-copy");
            CopyToolBarBtn.Clicked += this.copyMenu_Activated;
            SeparatorToolItem Sep2 = new SeparatorToolItem();
            ToolButton AboutToolBarBtn = new ToolButton("gtk-about");
            AboutToolBarBtn.Clicked += this.aboutMenu_Activated;

            this.toolbar.Add(OpenToolBarBtn);
            this.toolbar.Add(Sep1);
            this.toolbar.Add(CopyToolBarBtn);
            this.toolbar.Add(Sep2);
            this.toolbar.Add(AboutToolBarBtn);
        }

        private void CreateMenubar()
        {
            this.accelGroup = new AccelGroup();
            this.menubar = new MenuBar();
            MenuItem fileMenu = new MenuItem("_File");
            MenuItem editMenu = new MenuItem("_Edit");
            MenuItem helpMenu = new MenuItem("_Help");
            helpMenu.RightJustified = true;

            Menu fileSubMenu = new Menu();
            TearoffMenuItem fileMenuTearOff = new TearoffMenuItem();
            ImageMenuItem openMenu = new ImageMenuItem("gtk-open", accelGroup);
            openMenu.Activated += new System.EventHandler(openMenu_Activated);
            SeparatorMenuItem fileMenuSep = new SeparatorMenuItem();
            ImageMenuItem exitMenu = new ImageMenuItem("gtk-quit", accelGroup);
            exitMenu.Activated += new System.EventHandler(exitMenu_Activated);
            fileSubMenu.Add(fileMenuTearOff);
            fileSubMenu.Add(openMenu);
            fileSubMenu.Add(fileMenuSep);
            fileSubMenu.Add(exitMenu);
            fileMenu.Submenu = fileSubMenu;

            Menu editSubMenu = new Menu();
            ImageMenuItem copyMenu = new ImageMenuItem("gtk-copy", accelGroup);
            copyMenu.Activated += new System.EventHandler(copyMenu_Activated);
            TearoffMenuItem editMenuTearOff = new TearoffMenuItem();
            editSubMenu.Add(editMenuTearOff);
            editSubMenu.Add(copyMenu);
            editMenu.Submenu = editSubMenu;

            Menu helpSubMenu = new Menu();
            ImageMenuItem aboutMenu = new ImageMenuItem("gtk-about", accelGroup);
            TearoffMenuItem helpMenuTearOff = new TearoffMenuItem();
            helpSubMenu.Add(helpMenuTearOff);
            helpSubMenu.Add(aboutMenu);
            aboutMenu.Activated += new System.EventHandler(aboutMenu_Activated);
            helpMenu.Submenu = helpSubMenu;

            this.menubar.Add(fileMenu);
            this.menubar.Add(editMenu);
            this.menubar.Add(helpMenu);
        }

        void aboutMenu_Activated(object sender, System.EventArgs e)
        {
            using (Dialog dialog = new MessageDialog(this,
                                  DialogFlags.Modal | DialogFlags.DestroyWithParent,
                                  MessageType.Info,
                                  ButtonsType.Ok,
                                  "Text File Viewer - A simple text file viewer using gtk#\nDeveloped by Anuraj\nPowered by dotnetthoughts.net\n\nUnder GNU GPL v2."))
            {
                dialog.Title = "About";
                dialog.Run();
                dialog.Hide();
            }
        }

        private void copyMenu_Activated(object sender, System.EventArgs e)
        {
            Clipboard clipboad = this.textView.GetClipboard(Gdk.Selection.Clipboard);
            this.textView.Buffer.CopyClipboard(clipboad);
        }

        void exitMenu_Activated(object sender, System.EventArgs e)
        {
            Application.Quit();
        }
        FileChooserDialog dlg;
        private void openMenu_Activated(object sender, System.EventArgs e)
        {
            dlg =
                new FileChooserDialog("Select Text File", this, FileChooserAction.Open, "");
            dlg.AddButton("Open File", ResponseType.Ok);
            dlg.AddButton("Cancel", ResponseType.Cancel);

            FileFilter filter = new FileFilter();
            filter.AddPattern("*.txt");
            filter.AddPattern("*.*");
            dlg.Filter = filter;

            dlg.TypeHint = Gdk.WindowTypeHint.Dialog;
            dlg.SelectMultiple = false;
            dlg.WindowPosition = WindowPosition.Center;
            dlg.Parent = this;
            dlg.Modal = true;
            dlg.KeepAbove = true;
            dlg.DestroyWithParent = true;
            dlg.State = StateType.Normal;

            dlg.Response += new ResponseHandler(dlg_Response);
            dlg.DeleteEvent += new DeleteEventHandler(dlg_DeleteEvent);

            dlg.Run();
            dlg.Destroy();

        }

        private void dlg_DeleteEvent(object o, DeleteEventArgs args)
        {
            dlg.Destroy();
        }

        private void dlg_Response(object o, ResponseArgs args)
        {
            if (args.ResponseId == ResponseType.Ok)
            {
                this.Title = string.Format("{0} - {1}", this.title, System.IO.Path.GetFileName(dlg.Filename));
                using (StreamReader reader = new StreamReader(dlg.Filename, true))
                {
                    this.textView.Buffer.Text = reader.ReadToEnd();
                }
            }
            dlg.Destroy();
        }
    }
}

And run the application. Here is the screenshot, Text File Viewer running on my machine.

Text File Viewer using GTK#

Color Dialog. So I thought of implementing a WordPad like color picker. And I think I almost readed my goal. I need to try this in the Toolstrip dropdown too.

//On the Form load I am loading the colors to the Dropdown.
//You can also bind the p to the Dropdown.
Type t = typeof(Color);
PropertyInfo[] p = t.GetProperties();
foreach (PropertyInfo item in p)
{
    if (item.PropertyType.FullName.Equals("System.Drawing.Color", StringComparison.CurrentCultureIgnoreCase))
    {
        this.comboBox1.Items.Add(item.Name);
    }
}

And I set the Dropdown’s DrawMode property to “OwnerDrawFixed”. And in the DrawItem event of the Dropdown I wrote the code.

if (e.Index != -1)
{
    e.DrawBackground();
    e.Graphics.FillRectangle(GetCurrentBrush(comboBox1.Items[e.Index].ToString()), e.Bounds);
    Font f = comboBox1.Font;
    e.Graphics.DrawString(comboBox1.Items[e.Index].ToString(), f, Brushes.Black, e.Bounds, StringFormat.GenericDefault);
    e.DrawFocusRectangle();
}

And the GetCurrentBrush() function returns the Brush for painting the rectangle. You can write the code in the DrawItem event too, but initialy I thought about setting the font color using the same color. But later that idea changed.

private Brush GetCurrentBrush(string colorName)
{
    return new SolidBrush(Color.FromName(colorName));
}

One issue I found in this code is, for black color, I can’t see the color name. And here is the screenshot of Color Picker Dropdown running on my machine.

Color Picker Dropdown screenshot

using System.Net;

///
/// Checks the file exists or not.
///
/// The URL of the remote file.
/// True : If the file exits, False if file not exists
private bool RemoteFileExists(string url)
{
    try
    {
        //Creating the HttpWebRequest
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        //Setting the Request method HEAD, you can also use GET too.
        request.Method = "HEAD";
        //Getting the Web Response.
        HttpWebResponse response = request.GetResponse() as HttpWebResponse;
        //Returns TURE if the Status code == 200
        return (response.StatusCode == HttpStatusCode.OK);
    }
    catch
    {
        //Any exception will returns false.
        return false;
    }
}

You can also use WebClient class for the same purpose. Like this.

using System.Net;

///
/// Checks the file exists or not.
///
/// The URL of the remote file.
/// True : If the file exits, False if file not exists
private bool RemoteFileExists(string url)
{
    bool result = false;
    using (WebClient client = new WebClient())
    {
        try
        {
            Stream stream = client.OpenRead(url);
            if (stream != null)
            {
                result = true;
            }
            else
            {
                result = false;
            }
        }
        catch
        {
            //Any exception will returns false.
            result = false;
        }
    }
    return result;
}

Internally WebClient is using the HttpWebRequest and HttpWebResponse classes, so it is good to use the first method.