private ExpressionObserver CreateDataContexObserver(
IPerspexObject target,
string path,
bool targetIsDataContext)
{
Contract.Requires <ArgumentNullException>(target != null);
if (!targetIsDataContext)
{
var update = target.GetObservable(Control.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.DataContextProperty),
path,
update);
return(result);
}
else
{
return(new ExpressionObserver(
target.GetObservable(Visual.VisualParentProperty)
.OfType <IPerspexObject>()
.Select(x => x.GetObservable(Control.DataContextProperty))
.Switch(),
path));
}
}
/// <summary>
/// Gets an observable for a <see cref="PerspexProperty"/>.
/// </summary>
/// <param name="o">The object.</param>
/// <param name="property">The property.</param>
/// <returns>An observable.</returns>
public static IObservable <object> GetObservable(this IPerspexObject o, PerspexProperty property)
{
Contract.Requires <ArgumentNullException>(o != null);
Contract.Requires <ArgumentNullException>(property != null);
return(new PerspexObservable <object>(
observer =>
{
EventHandler <PerspexPropertyChangedEventArgs> handler = (s, e) =>
{
if (e.Property == property)
{
observer.OnNext(e.NewValue);
}
};
observer.OnNext(o.GetValue(property));
o.PropertyChanged += handler;
return Disposable.Create(() =>
{
o.PropertyChanged -= handler;
});
},
GetDescription(o, property)));
}
private ExpressionObserver CreateTemplatedParentObserver(
IPerspexObject target,
string path)
{
Contract.Requires <ArgumentNullException>(target != null);
var update = target.GetObservable(Control.TemplatedParentProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.TemplatedParentProperty),
path,
update);
return(result);
}
private ExpressionObserver CreateDataContexObserver(
IPerspexObject target,
string path,
bool targetIsDataContext,
object anchor)
{
Contract.Requires <ArgumentNullException>(target != null);
if (!(target is IControl))
{
target = anchor as IControl;
if (target == null)
{
throw new InvalidOperationException("Cannot find a DataContext to bind to.");
}
}
if (!targetIsDataContext)
{
var update = target.GetObservable(Control.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.DataContextProperty),
path,
update);
return(result);
}
else
{
return(new ExpressionObserver(
target.GetObservable(Visual.VisualParentProperty)
.OfType <IPerspexObject>()
.Select(x => x.GetObservable(Control.DataContextProperty))
.Switch(),
path));
}
}
private ExpressionObserver CreateTemplatedParentObserver(
IPerspexObject target,
string path)
{
Contract.Requires<ArgumentNullException>(target != null);
var update = target.GetObservable(Control.TemplatedParentProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.TemplatedParentProperty),
path,
update);
return result;
}
private ExpressionObserver CreateDataContexObserver(
IPerspexObject target,
string path,
bool targetIsDataContext)
{
Contract.Requires<ArgumentNullException>(target != null);
if (!targetIsDataContext)
{
var update = target.GetObservable(Control.DataContextProperty)
.Skip(1)
.Select(_ => Unit.Default);
var result = new ExpressionObserver(
() => target.GetValue(Control.DataContextProperty),
path,
update);
return result;
}
else
{
return new ExpressionObserver(
target.GetObservable(Visual.VisualParentProperty)
.OfType<IPerspexObject>()
.Select(x => x.GetObservable(Control.DataContextProperty))
.Switch(),
path);
}
}
