Complete set: Intro to C - Bill Buchanan

We keep a record of the country that is currently on display
//We do this so that we can "unsubscribe" it when the user
//selects a different item
Country CurrentlyFocussed = null;
Country.changeHandler CurrentlyFocussedCH = null;
//This is the action that causes the subject of the detail panel
//to change
private void worldLB_SelectedIndexChanged(object sender, System.EventArgs
e)
{
//Put details of the currently selected country
//in the detail text boxes
Country c =
world[worldLB.SelectedIndex] as Country;
ShowDetailsOfCountry(c,e);
//Now we want to subscribe to the OnChange event for this
//country.
//First we must unsubscribe whoever was registered before
if (CurrentlyFocussed!=null)
CurrentlyFocussed.OnChange -= CurrentlyFocussedCH;
//We create a new handler
CurrentlyFocussedCH = new
cia.Country.changeHandler(ShowDetailsOfCountry);
//We subscribe our new handler to the OnChange event of c
c.OnChange += CurrentlyFocussedCH;
//Remember the currently focussed item so we can unsubscribe
CurrentlyFocussed = c;
duction to .NET
Intro
}
//Show the user which record we are on
label6.Text = String.Format("{0}/{1}",
worldLB.SelectedIndex.ToString(),
worldLB.Items.Count);
Agilent .NET Course: Module 10,page
10