How to use AddChildItemBinded in C#?

I'm using c#.

I define a field named nData, and a property named Data like this:

private int nData = 0;         public int Data         {             get { return nData; }             set             {                 nData = value;                 System.Diagnostics.Debug.WriteLine(nData);             }         }

in the Form_Load function:

XtremePropertyGrid.PropertyGridItem root = PropertyGrid.AddCategory("a");             root.AddChildItemBinded(XtremePropertyGrid.PropertyItemType.PropertyItemNumber, this, "nData");

but the second line of the Form_Load code snippet throws an InvalidCastException, and says "Specified cast is not valid".

if  i change the third parameter of the second line to "Data", I still get the same error.

so, my question is, is it possible to use AddChildItemBinded in C#?
If it's possible, any sample available?

thanks.

you can get my project here:
http://python.leojay.googlepages.com/pgtest.zip

it's strange that, in your PropertyGrid sample, my code works.
but in a new project, it doesn't.
i don't know why. :(

thanks, that works.

is it possible to add some specific description in the thrown exception?
"Specified cast is not valid" is really not a good hint.