Changing the designer DefaultValue for a Property within a Property (Nested Property)

Changing the designer DefaultValue for a Property within a Property (Nested Property)

Hi,

I have an inherited control that derives from a control from a vendor. 
Let's call the vendor control VC and my inherited control myVC.

VC has a property Calendar which itself has various other properties such as 
BackColor.  So to access in code from myVC i would use 
this.Calendar.BackColor syntax.

The vendor has changed the default value for Calendar.BackColor property and 
I want to be able to override the default value with the prior default in 
myVC.

I'm not sure how to do this.  I was looking at the ShouldSerializeXXXX and 
ResetXXXX methods but I don't know how to make them work with nested 
properties.

I tried this could but it did not work.

  private bool ShouldSerializeCalendar_BackColor()
  {
   return Calendar.BackColor != SystemColors.Window;
  }

  private void ResetCalendar_BackColor()
  {
   Calendar.BackColor = SystemColors.Window;
  }

Is this possible and if so how would one go about implementing in the 
derived class?
--
Gregg Walker

date: Wed, 7 May 2008 16:38:23 -0700 author: Gregg Walker am

RE: Changing the designer DefaultValue for a Property within a Property (Nested Property)

Hi Gregg,

Firstly, to set a default value for a property of a class, we set the value 
of this property in the class's constructor first and then use the 
DefaultValueAttribute on the property to specify the default value. In the 
Properties window, any values other than the default value of the property 
will shown in a bold font.

Secondly, if a property is overriable, we can derive from the class and 
override the property. Change the initial value of the property in the 
derived class's constructor and adorn the DefaultAttribute on the override 
property to specify the new default value so as to change the default value 
of the property. 

To your question, if the Calendar property is overriable in the VC class, 
you can add a new property in the MyVC class to hide the Calendar property. 
The following is a sample to do this.

public partial class VC : UserControl
    {
        public VC()
        {
            InitializeComponent();
            calendar = new MonthCalendar();           
        }
        private MonthCalendar calendar;

        [TypeConverter(typeof(ExpandableObjectConverter)), 
DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        public virtual MonthCalendar Calendar
        {
            get { return calendar; }
            set { calendar = value; }
        }        
    }

public class DerivedType:MonthCalendar
    {
        public DerivedType()
        {
            BackColor = Color.Red;
        }
        [DefaultValue(typeof(Color),"Red")]
        public override Color BackColor
        {
            get
            {
                return base.BackColor;
            }
            set
            {
                base.BackColor = value;
            }
        }
    }

public partial class MyVC : VC
 {
        public MyVC()
        {
            InitializeComponent();
            calendar = new DerivedType();
        }
        private DerivedType calendar;

        
[TypeConverter(typeof(ExpandableObjectConverter)),DesignerSerializationVisib
ility(DesignerSerializationVisibility.Content)]
        public new DerivedType Calendar
        {
            get { return calendar; }
            set { calendar = value; }
        }
}

At last, the ShouldSerialize*** method is used by designer to determine 
whether the specified property should be serialized in the 
InitializeComponent method. The Reset*** method is used by the designer to 
reset the property to the default value in the Properties window. The 
DefaultValueAttribute does the all the work these two methods do.

Hope this helps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and 
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date: Thu, 08 May 2008 11:16:50 GMT author: (Linda Liu[MSFT])