Question

I’m trying to edit complex objects in a PropertyGrid control. I add the ExpandableObjectConverter (or my own subclass when I need it) as the TypeConverter and it works fine.

The one thing I can’t seem to figure out is this. The object itself will have its .ToString() representation next to it in the Grid. Then when I expand the object the attributes have the same. All can be editable. I want to disable editing of the ToString() object field, but keep the attributes editable.

So in the PropertyGrid it would look like this;

+ Color      {(R,G,B,A) = (255,255,255,255)}  --uneditable
     Alpha   255                              --editable
     Blue    255                              --editable
     Green   255                              --editable
     Red     255                              --editable

So far I haven’t found a way to do this. If I try to make it ReadOnly the entire object becomes read only. If I specify my own ExpandableObjectConverter and state it cannot convert from a string, if the string is edited in the PropertyGrid it will still try to cast and then fail.

I essentially just want it so I can stop end users from editing the string and forcing them to edit the individual attributes instead, so that I don’t have to write a string parser for every single class.

Is this possible, or is there another way of doing this I just haven’t thought of?

Answer 1

This seems to do the trick:

[TypeConverter(typeof (Color.ColorConverter))]
public struct Color
{
    private readonly byte alpha, red, green, blue;
    public Color(byte alpha, byte red, byte green, byte blue)
    {
        this.alpha = alpha;
        this.red = red;
        this.green = green;
        this.blue = blue;
    }
    public byte Alpha { get { return alpha; } }
    public byte Red { get { return red; } }
    public byte Green { get { return green; } }
    public byte Blue { get { return blue; } }
    public override string ToString()
    {
        return string.Format("{{(R,G,B,A) = ({0},{1},{2},{3})}}", Red, Green, Blue, Alpha);
    }
    private class ColorConverter : ExpandableObjectConverter
    {
        public override bool GetCreateInstanceSupported(ITypeDescriptorContext context)
        {
            return true;
        }
        public override object CreateInstance(ITypeDescriptorContext context, IDictionary propertyValues)
        {
            return new Color((byte)propertyValues["Alpha"], (byte)propertyValues["Red"],
                             (byte) propertyValues["Green"], (byte) propertyValues["Blue"]);
        }
    }
}