/// <summary>
/// Tracks a named control relative to another control.
/// </summary>
/// <param name="relativeTo">
/// The control relative from which the other control should be found.
/// </param>
/// <param name="name">The name of the control to find.</param>
public static IObservable <ILogical> Track(ILogical relativeTo, string name)
{
var attached = Observable.FromEventPattern <LogicalTreeAttachmentEventArgs>(
x => relativeTo.AttachedToLogicalTree += x,
x => relativeTo.AttachedToLogicalTree -= x)
.Select(x => ((ILogical)x.Sender).FindNameScope())
.StartWith(relativeTo.FindNameScope());
var detached = Observable.FromEventPattern <LogicalTreeAttachmentEventArgs>(
x => relativeTo.DetachedFromLogicalTree += x,
x => relativeTo.DetachedFromLogicalTree -= x)
.Select(x => (INameScope)null);
return(attached.Merge(detached).Select(nameScope =>
{
if (nameScope != null)
{
var registered = Observable.FromEventPattern <NameScopeEventArgs>(
x => nameScope.Registered += x,
x => nameScope.Registered -= x)
.Where(x => x.EventArgs.Name == name)
.Select(x => x.EventArgs.Element)
.OfType <ILogical>();
var unregistered = Observable.FromEventPattern <NameScopeEventArgs>(
x => nameScope.Unregistered += x,
x => nameScope.Unregistered -= x)
.Where(x => x.EventArgs.Name == name)
.Select(_ => (ILogical)null);
return registered
.StartWith(nameScope.Find <ILogical>(name))
.Merge(unregistered);
}
else
{
return Observable.Return <ILogical>(null);
}
}).Switch());
}