internal static Func <object, IObservable <Unit> > CreatePropertyChangedFactory(this MemberExpression source)
{
var property = source.GetProperty();
var inpc = typeof(INotifyPropertyChanged).GetTypeInfo().IsAssignableFrom(property.DeclaringType.GetTypeInfo());
return(t =>
{
if (t == null)
{
return Observable <Unit> .Never;
}
if (!inpc)
{
return Observable.Return(Unit.Default);
}
return Observable.FromEventPattern <PropertyChangedEventHandler, PropertyChangedEventArgs>
(
handler => ((INotifyPropertyChanged)t).PropertyChanged += handler,
handler => ((INotifyPropertyChanged)t).PropertyChanged -= handler
)
.Where(args => args.EventArgs.PropertyName == property.Name)
.Select(args => Unit.Default);
});
}
internal static Func <object, object> CreateValueAccessor(this MemberExpression source)
{
// create an expression which accepts the parent and returns the child
var property = source.GetProperty();
var method = property.GetMethod;
if (method is null)
{
throw new ArgumentException("The property does not have a valid get method.", nameof(source));
}
if (source.Expression is null)
{
throw new ArgumentException("The source expression does not have a valid expression.", nameof(source));
}
// convert the parameter i.e. the declaring class to an object
var parameter = Expression.Parameter(typeof(object));
var converted = Expression.Convert(parameter, source.Expression.Type);
// call the get value of the property and box it
var propertyCall = Expression.Call(converted, method);
var boxed = Expression.Convert(propertyCall, typeof(object));
var accessorExpr = Expression.Lambda <Func <object, object> >(boxed, parameter);
return(accessorExpr.Compile());
}
internal static Func <object, IObservable <Unit> > CreatePropertyChangedFactory(this MemberExpression source)
{
var property = source.GetProperty();
if (property.DeclaringType is null)
{
throw new ArgumentException("The property does not have a valid declaring type.", nameof(source));
}
var notifyPropertyChanged = typeof(INotifyPropertyChanged).GetTypeInfo().IsAssignableFrom(property.DeclaringType.GetTypeInfo());
return(t =>
{
if (t is null)
{
return Observable <Unit> .Never;
}
if (!notifyPropertyChanged)
{
return Observable.Return(Unit.Default);
}
return Observable.FromEventPattern <PropertyChangedEventHandler, PropertyChangedEventArgs>(handler => ((INotifyPropertyChanged)t).PropertyChanged += handler, handler => ((INotifyPropertyChanged)t).PropertyChanged -= handler).Where(args => args.EventArgs.PropertyName == property.Name).Select(_ => Unit.Default);
});
}
internal static Func <object, object> CreateValueAccessor(this MemberExpression source)
{
//create an expression which accepts the parent and returns the child
var property = source.GetProperty();
var method = property.GetMethod;
//convert the parameter i.e. the declaring class to an object
var parameter = Expression.Parameter(typeof(object));
var converted = Expression.Convert(parameter, source.Expression.Type);
//call the get value of the property and box it
var propertyCall = Expression.Call(converted, method);
var boxed = Expression.Convert(propertyCall, typeof(object));
var accessorExpr = Expression.Lambda <Func <object, object> >(boxed, parameter);
var accessor = accessorExpr.Compile();
return(accessor);
}
