How can I bind to a helper property in Silverlight
- by Matt
For the sake of argument, here's a simple person class
public class Person : DependencyObject, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public static readonly DependencyProperty FirstNameProperty =
DependencyProperty.Register( "FirstName",
typeof ( string ),
typeof ( Person ),
null );
public static readonly DependencyProperty LastNameProperty =
DependencyProperty.Register( "LastName",
typeof( string ),
typeof( Person ),
null );
public string FirstName
{
get
{
return ( string ) GetValue( FirstNameProperty );
}
set
{
SetValue( FirstNameProperty, value );
if(PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs( "FirstName" ));
}
}
public string LastName
{
get
{
return ( string ) GetValue( LastNameProperty );
}
set
{
SetValue( LastNameProperty, value );
if ( PropertyChanged != null )
PropertyChanged( this, new PropertyChangedEventArgs( "LastName" ) );
}
}
}
I want to go about creating a readonly property like this
public string FullName
{
get { return FirstName + " " + LastName; }
}
How does binding work in this scenario? I've tried adding a DependancyProperty and raised the PropertyChanged event for the fullname. Basically I just want to have a property that I can bind to that returns the fullname of a user whenever the first or last name changes. Here's the final class I'm using with the modifications.
public class Person : DependencyObject, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public static readonly DependencyProperty FirstNameProperty =
DependencyProperty.Register( "FirstName",
typeof ( string ),
typeof ( Person ),
null );
public static readonly DependencyProperty LastNameProperty =
DependencyProperty.Register( "LastName",
typeof( string ),
typeof( Person ),
null );
public static readonly DependencyProperty FullNameProperty =
DependencyProperty.Register( "FullName",
typeof( string ),
typeof( Person ),
null );
public string FirstName
{
get
{
return ( string ) GetValue( FirstNameProperty );
}
set
{
SetValue( FirstNameProperty, value );
if ( PropertyChanged != null )
{
PropertyChanged( this, new PropertyChangedEventArgs( "FirstName" ) );
PropertyChanged( this, new PropertyChangedEventArgs( "FullName" ) );
}
}
}
public string LastName
{
get
{
return ( string ) GetValue( LastNameProperty );
}
set
{
SetValue( LastNameProperty, value );
if ( PropertyChanged != null )
{
PropertyChanged( this, new PropertyChangedEventArgs( "LastName" ) );
PropertyChanged( this, new PropertyChangedEventArgs( "FullName" ) );
}
}
}
public string FullName
{
get { return GetValue( FirstNameProperty ) + " " + GetValue( LastNameProperty ); }
}
}
