Prevent Size property from being serialized when it's equal to default value

Question

I'm trying to create my own class from System.Windows.Forms.Button

public class MyButton : Button
{

    public MyButton() : base()
    {
        Size = new Size(100, 200);
    }

    [DefaultValue(typeof(Size), "100, 200")]
    public new Size Size { get => base.Size; set => base.Size = value; }
}

I have a problem with Designer.cs behavior - default value is not working properly.

I expect, that when MyButton is added to form, it has Size of 100x200, but it is not set through Designer.cs, so when in MyButton constructor I change Size to 200x200 (also for DefaultValue) all MyButton get new size. Of course, when I change the size in Design Mode it should then be added to Designer.cs and not affected by later changes in MyButton class.

Although, in current configuration Size is always added to Designer.cs.

I tried different approaches (with Invalidate() or DesignerSerializationVisibility) but with no luck.

I want to Stop Size from being serialized when it is equal to DefaultValue. For example when it is dropped from toolbox to form - it is instantly serialized in designer, while I don't want that - only serialize when I change the size.

Answer 1

For some reason, the ControlDesigner replaces Size property in the PreFilterProperties with a custom property descriptor which its ShouldSerializeValue always returns true. It means the Size property will be always serialized unless you decorate it with designer serialization visibility attribute having hidden as value.

You can change the behavior by restoring the original property descriptor:

using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.Design;

[Designer(typeof(MyButtonDesigner))]
public class MyButton : Button
{
    protected override Size DefaultSize
    {
        get { return new Size(100, 100); }
    }

    //Optional, just to enable Reset context menu item
    void ResetSize()
    {
        Size = DefaultSize;
    }
}
public class MyButtonDesigner : ControlDesigner
{
    protected override void PreFilterProperties(IDictionary properties)
    {
        var s = properties["Size"];
        base.PreFilterProperties(properties);
        properties["Size"] = s;
    }
}