I have an object `MyPerson` with the properties `FirstName`, `LastName`, and `FullName` where 

```
public string FullName
{
    get {return LastName + " " + FirstName;}
    set {...}
}

```

I bind the MyPerson to a `UserControl`, in which I bind FirstName, LastName and FullNAme to 3 texboxes.

Now, when I modify the FirstName or LastName I need to indicate to the UserControl to "update" the FullName.

What should be this "update" command?

Silverlight 4