Issues changing default backcolor in a usercontrol

Question

I am creating a custom control with a black background but have some issues with the designer. Truth to be told I have a base control class that inherits from UserControl and then some subclasses that represent the final controls that I will use in my GUI. In that base class I override the BackColor property, add the DefaultValue attribute and set the default value to BackColor in the constructor. As an example my code looks something like this:

public partial class MyControl1 : UserControl
{
    public MyControl1()
    {
        InitializeComponent();
        BackColor = Color.Black;            
    }

    [DefaultValue(typeof(Color),"Black")]
    public override Color BackColor
    {
        get
        {
            return base.BackColor;
        }
        set
        {
            base.BackColor = value;
        }
    }
}

...

public partial class MyControl2 : MyControl1
{
    public MyControl2()
    {
        InitializeComponent();
    }
}

The thing is every time I open the designer for MyControl2, BackColor in the properties dialog reverts to System.Drawing.SystemColors.Control and my control is painted grey. If I invoke Reset on BackColor it properly returns to Color.Black, though. Also, the designer doesn't serialize the change to System.Drawing.SystemColors.Control until I make another change to the control.

So, what did I try?

• I thought it could be related to BackColor being an ambient property so I tried adding the attribute AmbientValue(false). Of course it didn't work.

• I tried erasing the overridden property, leaving only BackColor=Color.Black in the constructor. Surprisingly it fixed the problem with the designer but now resetting the property reverted it to a default value of System.Drawing.SystemColors.Control. Overriding ResetBackColor() didn't solve this last problem.

By the way, I am working under Visual Studio 2010 and my project was created as a .NET 2.0 Windows Forms Application.

I would be glad whether anyone could help me to find whatever is wrong in my code. It is not something that would prevent me from finishing the project but it is pretty annoying. Thank you very much in advance!

Answer 1

This may help - there appears to be some voodoo in the winforms designer (a bit like the XML serializer) that will look for properties which are named a specific way because the DefaultValue doesn't work as you might expect:

The following is an example from another post, I know you are not subclassing a DataGridView, but the principle ought to be the same.

public class MyGridView : DataGridView {
    public MyGridView() {
        this.BackgroundColor = DefaultBackgroundColor;
    }
    public new Color BackgroundColor {
        get { return base.BackgroundColor; }
        set { base.BackgroundColor = value;  }
    }
    private bool ShouldSerializeBackgroundColor() {
        return !this.BackgroundColor.Equals(DefaultBackgroundColor);
    }
     private void ResetBackgroundColor() {
        this.BackgroundColor = DefaultBackgroundColor;
    }
    private static Color DefaultBackgroundColor {
        get { return Color.Red; }
    }
}

Incidently - this isn't my code - it's some more pure genius from Hans Passant... link to original with a full explanation: https://stackoverflow.com/a/20838280/685341