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Custom Controls Design Time Support Part 8: Implementing UITypeEditor

by Amr Elsehemy 18. January 2008 11:15

In the previous post I gave a brief introduction on what is a UITypeEditor and what you can get from using it, this part I will show you how to implement one.

So here are the steps:

Define a class that derives from System.Drawing.Design.UITypeEditor.
Override GetEditStyle to return a supported UITypeEditorEditStyle.
Override EditValue and pass any controls necessary to the IWindowsFormsEditorService.
Override GetPaintValueSupported.
Override PaintValue if the editor supports painting.
Override IsDropDownResizable if the editor is resiazble.

Now we will go through the steps one by one, the example I will introduce here will be another ColorEditor, I will use the ColorWheel introduced and explained in this MSDN magazine article.

The final editor that we will make will look like this

Step 1

public class ColorWheelEditor : UITypeEditor

Step 2

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

Step 3

public override object EditValue(System.ComponentModel.ITypeDescriptorContext context, IServiceProvider provider, object value)
{
   IWindowsFormsEditorService iwefs = provider.GetService(typeof(IWindowsFormsEditorService)) as IWindowsFormsEditorService;
   Color c;
   using (ColorWheelContainer cwc = new ColorWheelContainer(iwefs))
   {
     cwc.Color = (Color)value;
     iwefs.DropDownControl(cwc);
     if (cwc.Result == DialogResult.OK)
     {
       c = cwc.Color;
     }
     else
     {
       c = (Color)value;
     }
   }
  return c;
}

Here, I need to introduce you to the IWindowsFormsEditorService .

Namespace

System.Windows.Forms.Design

Assembly

System.Windows.Forms

Methods

DropDownControl	accepts a parameter of type control that will be shown the drop down, works when the edit style is UITypeEditorEditStyle.DropDown.
CloseDropDown	when called closes the drop down, works when the edit style is UITypeEditorEditStyle.DropDown.
ShowDialog	accepts a parameter of type Form, which represents the dialog that will be opened, works when the edit style is UITypeEditorEditStyle.Modal.

Step 4

public override bool GetPaintValueSupported(System.ComponentModel.ITypeDescriptorContext context)
{
return true; // we will use the picked color and fill the rectangle.
}

Step 5

public override void PaintValue(PaintValueEventArgs e)
{
Color c = (Color)e.Value;
e.Graphics.FillRectangle(new SolidBrush(c), e.Bounds);
}

Step 6

public override bool IsDropDownResizable
{
   get
   {
     return false;//we don't want it to be resizable
   }
}

Now don't forget to associate the editor with the color property using the Editor attribute.

[Editor(typeof(ColorWheelEditor),typeof(UITypeEditor))]
public Color ColorProperty

In this part I showed how to implement a UITypeEditor that appears in a Drop Down. See you soon.

ColorWheelEditor.zip (13.99 kb)

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