Comments on Eric De C#: How to use INotifyPropertyChanged, the type-safe w...

screw it... the angled brackets got eaten away.. (...

2010-05-03T08:24:31.254-04:00

screw it... the angled brackets got eaten away.. (I'll try square ones instead) :

public abstract class ViewModelBase[TConcreteType] : INotifyPropertyChanged
{
protected void NotifyPropertyChanged(Expression[Func[TConcreteType, object]] member)
{
if (member == null)
{
throw new ArgumentNullException("member");
}
if (this.PropertyChanged == null)
{
return;
}
this.PropertyChanged(this, new PropertyChangedEventArgs(ExpressionUtil.MemberName[TConcreteType](member)));
}

public event PropertyChangedEventHandler PropertyChanged;

public bool IsPropertyName(Expression[Func[TConcreteType, object]] property, string propertyName)
{
return ExpressionUtil.MemberName[TConcreteType](property) == propertyName;
}
}

and

public static class ExpressionUtil
{
public static string MemberName[T](Expression[Func[T, object]] unaryExpression)
{
var unaryExpr = (UnaryExpression)unaryExpression.Body;
var memberExpr = (MemberExpression)unaryExpr.Operand;
return memberExpr.Member.Name;
}
}

2010-05-03T07:50:18.225-04:00

This comment has been removed by the author.

Hi, great idea. I got inspired by that and wrote s...

2009-08-01T09:11:41.395-04:00

Hi, great idea.
I got inspired by that and wrote something about it.
Have a look at http://gfoidl.spaces.live.com/blog/cns!36D34E66505CE4AF!201.entry

Altought it's written in German language the code should be readable.
It's very little code needed and shows a variant with reflection where even no arguments are needed.

See my next post to find a solution I think worth ...

2009-07-22T18:17:14.157-04:00

See my next post to find a solution I think worth trying.

Nope, because you can't raise the event from y...

2009-07-22T10:57:46.212-04:00

Nope, because you can't raise the event from your extension method.

I think that you could just write the extension me...

2009-07-22T08:23:08.062-04:00

I think that you could just write the extension method for the INotifyPropertyChanged interface, then do:

"this.Raise(()=>Data)" and the inheritance problems go away.

You are right. You need PropertyChanged event defi...

2009-07-22T07:28:56.974-04:00

You are right. You need PropertyChanged event defined in every derived classes, but it it's not so good because they will "hide" the base implementation.

Another way to do this would be to define a virtual method on the base class that take a "Expression Of (Func Of object)" and use it to call the PropertyChanged event.

I used to implement my INPC interface like this:
#region INotifyPropertyChanged Members

private string[] GetPropertiesList()
{
Type t = GetType();
PropertyInfo[] properties =
t.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty);

var propList = new string[properties.Length];
for (int i = 0; i < properties.Length; i++)
propList[i] = properties[i].Name;
return propList;
}

public void RaisePropertyChanged(params string[] properties)
{
if (properties.Length == 0)
properties = GetPropertiesList();

foreach (string property in properties)
OnPropertyChanged(new PropertyChangedEventArgs(property));
}

private void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (PropertyChanged != null)
PropertyChanged(this, e);

OnPropertyChangedCore(e);
}

protected virtual void OnPropertyChangedCore(PropertyChangedEventArgs args) {}

public event PropertyChangedEventHandler PropertyChanged;

#endregion

Maybe you did not understand. Anyways, I tried it,...

2009-07-22T07:18:01.839-04:00

Maybe you did not understand. Anyways, I tried it, and it does NOT work (as I expected).

What I mean is something like:

public class SpecialModel : Model
{
private string _data2;

public string Data2
{
get { return _data2; }
set
{
_data2 = value;
PropertyChanged.Raise(() => Data2);
}
}
}

The above will not compile. You will get: error CS0070: The event 'Model.PropertyChanged' can only appear on the left hand side of += or -= (except when used from within the type 'Model')

:|

Of course it works on inherited classes because it...

2009-07-22T06:50:16.911-04:00

Of course it works on inherited classes because it doesn't depend on inheritance.

Nice work :) Does this work in the inherited clas...

2009-07-22T02:15:22.908-04:00

Nice work :)

Does this work in the inherited class case?