Exemplarische Vorgehensweise: Implementieren eines Typ-Editors für die Benutzeroberfläche

// This defines the possible values for the MarqueeBorder
// control's LightShape property.
public enum MarqueeLightShape
{
    Square,
    Circle
}

    // This control provides the custom UI for the LightShape property
    // of the MarqueeBorder. It is used by the LightShapeEditor.
    public class LightShapeSelectionControl : System.Windows.Forms.UserControl
	{
        private MarqueeLightShape lightShapeValue = MarqueeLightShape.Square;
        private IWindowsFormsEditorService editorService = null;
        private System.Windows.Forms.Panel squarePanel;
		private System.Windows.Forms.Panel circlePanel;
		
		// Required designer variable.
		private System.ComponentModel.Container components = null;

        // This constructor takes a MarqueeLightShape value from the
        // design-time environment, which will be used to display
        // the initial state.
		public LightShapeSelectionControl( 
            MarqueeLightShape lightShape,
            IWindowsFormsEditorService editorService )
		{
			// This call is required by the designer.
			InitializeComponent();

            // Cache the light shape value provided by the 
            // design-time environment.
			this.lightShapeValue = lightShape;

            // Cache the reference to the editor service.
            this.editorService = editorService;

            // Handle the Click event for the two panels. 
			this.squarePanel.Click += new EventHandler(squarePanel_Click);
			this.circlePanel.Click += new EventHandler(circlePanel_Click);
		}

        protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
                // Be sure to unhook event handlers
                // to prevent "lapsed listener" leaks.
				this.squarePanel.Click -= 
                    new EventHandler(squarePanel_Click);
				this.circlePanel.Click -= 
                    new EventHandler(circlePanel_Click);

				if(components != null)
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

        // LightShape is the property for which this control provides
        // a custom user interface in the Properties window.
		public MarqueeLightShape LightShape
		{
			get
			{
				return this.lightShapeValue;
			}
			
			set
			{
				if( this.lightShapeValue != value )
				{
					this.lightShapeValue = value;
				}
			}
		}

        protected override void OnPaint(PaintEventArgs e)
		{
			base.OnPaint (e);

			using( 
				Graphics gSquare = this.squarePanel.CreateGraphics(),
				gCircle = this.circlePanel.CreateGraphics() )
			{	
                // Draw a filled square in the client area of
                // the squarePanel control.
				gSquare.FillRectangle(
                    Brushes.Red, 
                    0,
                    0,
                    this.squarePanel.Width,
                    this.squarePanel.Height
                    );

                // If the Square option has been selected, draw a 
                // border inside the squarePanel.
				if( this.lightShapeValue == MarqueeLightShape.Square )
				{
					gSquare.DrawRectangle( 
						Pens.Black,
						0,
						0,
						this.squarePanel.Width-1,
						this.squarePanel.Height-1);
				}

                // Draw a filled circle in the client area of
                // the circlePanel control.
				gCircle.Clear( this.circlePanel.BackColor );
				gCircle.FillEllipse( 
                    Brushes.Blue, 
                    0,
                    0,
                    this.circlePanel.Width, 
                    this.circlePanel.Height
                    );

                // If the Circle option has been selected, draw a 
                // border inside the circlePanel.
				if( this.lightShapeValue == MarqueeLightShape.Circle )
				{
					gCircle.DrawRectangle( 
						Pens.Black,
						0,
						0,
						this.circlePanel.Width-1,
						this.circlePanel.Height-1);
				}
			}	
		}

        private void squarePanel_Click(object sender, EventArgs e)
		{
			this.lightShapeValue = MarqueeLightShape.Square;
			
			this.Invalidate( false );

            this.editorService.CloseDropDown();
		}

		private void circlePanel_Click(object sender, EventArgs e)
		{
            this.lightShapeValue = MarqueeLightShape.Circle;

            this.Invalidate( false );

            this.editorService.CloseDropDown();
		}

		#region Component Designer generated code
		/// <summary> 
		/// Required method for Designer support - do not modify 
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
            this.squarePanel = new System.Windows.Forms.Panel();
            this.circlePanel = new System.Windows.Forms.Panel();
            this.SuspendLayout();
// 
// squarePanel
// 
            this.squarePanel.Location = new System.Drawing.Point(8, 10);
            this.squarePanel.Name = "squarePanel";
            this.squarePanel.Size = new System.Drawing.Size(60, 60);
            this.squarePanel.TabIndex = 2;
// 
// circlePanel
// 
            this.circlePanel.Location = new System.Drawing.Point(80, 10);
            this.circlePanel.Name = "circlePanel";
            this.circlePanel.Size = new System.Drawing.Size(60, 60);
            this.circlePanel.TabIndex = 3;
// 
// LightShapeSelectionControl
// 
            this.Controls.Add(this.squarePanel);
            this.Controls.Add(this.circlePanel);
            this.Name = "LightShapeSelectionControl";
            this.Size = new System.Drawing.Size(150, 80);
            this.ResumeLayout(false);

        }
		#endregion

		
	}

public override UITypeEditorEditStyle GetEditStyle(
System.ComponentModel.ITypeDescriptorContext context)
{
    return UITypeEditorEditStyle.DropDown;
}

public override object EditValue(
    ITypeDescriptorContext context,
    IServiceProvider provider,
    object value)
{
    if (provider != null)
    {
        editorService =
            provider.GetService(
            typeof(IWindowsFormsEditorService))
            as IWindowsFormsEditorService;
    }

    if (editorService != null)
    {
        LightShapeSelectionControl selectionControl =
            new LightShapeSelectionControl(
            (MarqueeLightShape)value,
            editorService);

        editorService.DropDownControl(selectionControl);

        value = selectionControl.LightShape;
    }

    return value;
}

// This method indicates to the design environment that
// the type editor will paint additional content in the
// LightShape entry in the PropertyGrid.
public override bool GetPaintValueSupported(
    ITypeDescriptorContext context)
{  
    return true;
}

// This method paints a graphical representation of the 
// selected value of the LightShpae property.
public override void PaintValue(PaintValueEventArgs e)
{   
    MarqueeLightShape shape = (MarqueeLightShape)e.Value;
    using (Pen p = Pens.Black)
    {
        if (shape == MarqueeLightShape.Square)
        {
            e.Graphics.DrawRectangle(p, e.Bounds);
        }
        else
        {
            e.Graphics.DrawEllipse(p, e.Bounds);
        }
    }   
}