how to stop loading page while selecting the values in DDL

no relationship both are in same page....,

just like selecting states after selecting country.

Try dis once....

suppose you have 2 classes one for each drop down list.

public class parent
{
public int Id {get;set;} //pk
public string name {get;set;}
}

public class child
{
public int Id {get;set;}  //pk
public string childname {get;set;} 
public virtual parent par {get;set;}
public int parId {get;set;}  //fk
}

public class mainwindow
{
context db=new context();
var result=from name in db.parentlist
               select name;

ddl1.selectedvaluepath="Id";    
ddl1.displaymemberpath="Name";
ddl1.itemssource=result.tolist();

}

private void ddl1_selectedvaluechanged(object sender, SelectionChangedEventArgs e)      //ddl1 item selected event
{

var val=ddl1.selectedvalue;

context db=new context();
var result=from n in db.childlist
               where id=val 
               select n;

ddl2.itemssource=result.tolist(); 
}