Custom Control: The property must be noted for the control

If the attribute is a string, int, or other class, the attribute is modified during design and saved during runtime.

If the property is a control, such as Label, the property is changed during design and restored during runtime, you can add

 

DesignerSerializationVisibility allows you to save settings at runtime, such:

? [DescriptionAttribute ("Get/set the second Label"), CategoryAttribute ("Custom"), DesignerSerializationVisibility (DesignerSerializationVisibility. Content)]
Public Label SecondLabel
{
Get {return label2 ;}
Set {label2 = value ;}
}

[DescriptionAttribute ("Get/set the second Label"), CategoryAttribute ("Custom"), DesignerSerializationVisibility (DesignerSerializationVisibility. Content)]
Public Label SecondLabel
{
Get {return label2 ;}
Set {label2 = value ;}
}