将控件属性保留到Designer.cs文件

Question

I have a custom control which contains a property of type PointF . When this control is added to a form and is saved, the designer.cs file doesn't say something like:

...
this.customControl.LocationF = new System.Drawing.PointF(50.0f, 50.0f);
...

Instead, it says this:

...
this.customControl.LocationF = ((System.Drawing.PointF)(resources.GetObject("customControl.LocationF")));
...

I've been trying to "persuade" this property to properly serialise to the designer file, and my search has turned up a couple of promising leads:

• DesignerSerializerAttribute , but I can't make sense of exactly what it's supposed to do, or how to use it.
• A TypeConverter which can convert to an InstanceDescriptor (looking at the example given by MSDN for Generating Code for Custom Types ).

I've followed the example given in the MSDN example, replacing Point with PointF and int with float , then my CustomControl looks like this:

public class CustomControl : Button
{ 
  [Category("Layout")]
  [TypeConverter(typeof(PointFConverter))]
  public PointF LocationF
  {
    get { return this.Location; }
    set { this.Location = new Point((int)value.X, (int)value.Y); }
  }
}

As far as I can see, this should work, but it seems to have no effect on how it's serialised to the designer file.

Something else I've just noticed - the PointFConverter isn't actually ever used when generating the designer.cs file - it's only used when reading or writing the value of the property in the properties box in design mode... Maybe this TypeConverter thing is a dead end...

In Short...

How do I make a control's property (specifically in this case a PointF type) serialise correctly to a form's designer.cs file?

Update

I'm now looking at a subclass of the CodeDomSerializer , which does change the designer.cs code (adding a comment as per the example on that page works) but it seems that I can only apply it to the CustomControl class as a whole, and try to modify the base serialization to replace the CodeCastExpression with a CodeObjectCreateExpression . This seems like a really messy way of doing things, though...

Answer 1

Create the following class:

public class MyPointF
{
    public float X { get; set; }
    public float Y { get; set; }
}

Use the following class definition for your CustomControl :

public class CustomButton : Button
{
    private MyPointF _locationF = new MyPointF() { X = 50, Y = 50 };

    [Category("Layout")]
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
    public MyPointF LocationF
    {
        get
        {
            return _locationF;
        }
        set
        {
            _locationF = value;
        }
    }
}

Sources:

• How to: Serialize Collections of Standard Types with the DesignerSerializationVisibilityAttribute
• Cannot modify the return value error c# .