How to add designer support for Point property on custom control?

Question

I have a custom control with a property called Offset that is type PointF.

I want to be able to edit the property from the Form Designer (it is currently disabled).

I read that I must add the EditorAttribute which points to a class derived from System.Drawing.Design.UITypeEditor.

It looks like there are quite a few built in types that derive from UITypeEditor already such as:

System.ComponentModel.Design.BinaryEditor
System.ComponentModel.Design.CollectionEditor
System.ComponentModel.Design.DateTimeEditor
System.ComponentModel.Design.MultilineStringEditor
System.ComponentModel.Design.ObjectSelectorEditor
System.Drawing.Design.ColorEditor
System.Drawing.Design.ContentAlignmentEditor
System.Drawing.Design.CursorEditor
System.Drawing.Design.FontEditor
System.Drawing.Design.FontNameEditor
System.Drawing.Design.IconEditor

... etc

I can't find one for editing a PointF or Point type. It seems like this functionality should already exist since .NET exposes Point/PointF types all the time in the designer.

I'm hoping I don't have to reinvent the wheel - I want to use the built in UITypeEditor type if it already exists.

Thanks.

Answer 1

You can add a property to a custom control of type Point that allows editing in the control's property grid using this code:

[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible),
 EditorBrowsable(EditorBrowsableState.Advanced),
 TypeConverter(typeof(PointConverter))]
public Point MyPointProperty { get; set; }

If you try the same sort of approach with a SizeF you'll find there's no built in .NET TypeConverter for a PointF. You can create your own though, I found one here (and copy and pasted most of the code below).

With a PointF TypeConverter you can write a property of type PointF that's editable in the property window:

[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible),
 EditorBrowsable(EditorBrowsableState.Advanced),
 TypeConverter(typeof(PointFConverter))]
public PointF MyPointFProperty { get; set; }

---

Here's the PointF type converter code found in the article linked above:

/// <summary>
/// PointFConverter
/// </summary>
public class PointFConverter : ExpandableObjectConverter
{
    /// <summary>
    /// Creates a new instance of PointFConverter
    /// </summary>
    public PointFConverter() {
    }

    /// <summary>
    /// Boolean, true if the source type is a string
    /// </summary>
    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) {
        if (sourceType == typeof(string)) return true;
        return base.CanConvertFrom(context, sourceType);
    }

    /// <summary>
    /// Converts the specified string into a PointF
    /// </summary>
    public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value) {
        if (value is string) {
            try {
                string s = (string)value;
                string[] converterParts = s.Split(',');
                float x = 0;
                float y = 0;
                if (converterParts.Length > 1) {
                    x = float.Parse(converterParts[0].Trim());
                    y = float.Parse(converterParts[1].Trim());
                } else if (converterParts.Length == 1) {
                    x = float.Parse(converterParts[0].Trim());
                    y = 0;
                } else {
                    x = 0F;
                    y = 0F;
                }
                return new PointF(x, y);
            } catch {
                throw new ArgumentException("Cannot convert [" + value.ToString() + "] to pointF");
            }
        }
        return base.ConvertFrom(context, culture, value);
    }

    /// <summary>
    /// Converts the PointF into a string
    /// </summary>
    public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType) {
        if (destinationType == typeof(string)) {
            if (value.GetType() == typeof(PointF)) {
                PointF pt = (PointF)value;
                return string.Format("{0}, {1}", pt.X, pt.Y);
            }
        }
        return base.ConvertTo(context, culture, value, destinationType);
    }
}