Aero TreeView like Windows Explorer – C#

Mit diesem Snippet, eine Modifikation der System.Windows.Forms.TreeView, könnt ihr eure TreeView wie die im Windows Explorer darstellen.

Das “Control” ist flackerfrei und unterstützt auch ältere Systeme vor Vista und Windows 7. Der “Windows Explorer”-Stil ist jedoch erst ab Vista verfügbar.

Einige Funktionen:

• Die “ShowPlusMinus”-Eigenschaft wird wie im Explorer ein- und ausgeblendet, sobald das Control den Fokus erhält bzw. verliert.
• Die horizontale Scrollbar entfällt, die TreeView scrollt automatisch.
• Die Markierung einer “Node” ist wie im Windows Explorer grafisch hochwertiger.
• Die TreeView ist flackerfrei.

Hier der Code der TreeViewAero.cs:

using System.ComponentModel;
using System.Drawing;
using System.Runtime.InteropServices;

namespace System.Windows.Forms
{
    /// <summary>
    /// A stylish treeview like the one from Windows Explorer 
    /// </summary>
    [DesignerCategory("Code")]
    [ToolboxBitmap(typeof(TreeView))]
    public class TreeViewAero : TreeView
    {
        public TreeViewAero()
        {
            // sets double buffering for flickerfree treeview
            base.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.UserPaint, true);

            // like the one in Windows Explorer
            base.ShowLines = false;
            base.HideSelection = false;
        }

        /// <summary>
        /// OnPaint-Method, modified for UserPaint-Flag at Style
        /// </summary>
        /// <param name="e">base PaintEventArgs</param>
        protected override void OnPaint(PaintEventArgs e)
        {
            if (GetStyle(ControlStyles.UserPaint))
            {
                // create new message
                Message m = new Message();

                // content handle
                m.HWnd = this.Handle;

                // message itself
                m.Msg = 0x0318; // WM_PRINTCLIENT message

                // params
                m.WParam = e.Graphics.GetHdc();
                m.LParam = (IntPtr)4; // PRF_CLIENT message

                // send this message
                DefWndProc(ref m);

                // release hdc
                e.Graphics.ReleaseHdc(m.WParam);
            }

            // do the basics
            base.OnPaint(e);
        }

        /// <summary>
        /// OnHandleCreated-Method
        /// </summary>
        /// <param name="e">base EventArgs</param>
        protected override void OnHandleCreated(EventArgs e)
        {
            // do the basics
            base.OnHandleCreated(e);

            // set the theme of this treeview from "explorer" (application name)
            NativeMethods.SetWindowTheme(base.Handle, "explorer", null);

            if (Environment.OSVersion.Version.Major > 5) // greater than xp
            {
                // send some messages for the stylish effects
                IntPtr lParam = (IntPtr)(NativeMethods.SendMessage(base.Handle, 0x112d, IntPtr.Zero, IntPtr.Zero).ToInt32() | 0x60);
                NativeMethods.SendMessage(base.Handle, 0x112c, IntPtr.Zero, lParam);
            }
        }

        /// <summary>
        /// CreateParams-Property
        /// </summary>
        protected override CreateParams CreateParams
        {
            get
            {
                // get base params
                CreateParams createParams = base.CreateParams;

                if (Environment.OSVersion.Version.Major > 5) // greater than xp
                {
                    // a bitwise logical OR operation
                    createParams.Style |= 0x8000;
                }

                // return the modified value
                return createParams;
            }
        }
    }

    public abstract class NativeMethods
    {
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

        [DllImport("uxtheme.dll", ExactSpelling = true, CharSet = CharSet.Unicode)]
        public static extern int SetWindowTheme(IntPtr hWnd, String pszSubAppName, String pszSubIdList);
    }
}