Help for a DataTemplate

Hi, I have a problem with creating a DataTemplate for a PropertyGrid.
Should I see an object that contains a collection of my class MyClass dimensioned on the number of elements of a second collection MyClass2 not contained in the object displayed in the PropertyGrid.

var a = new ObservableCollection <MyCLass2> ();
a.Add (new MyClass2 ());
a.Add (new MyClass2 ());
...
var b = new ObservableCollection <MyClass> ();
for (int i = 0; i <a.Count (); i + +)
{
   b.add (new MyClass ());
}

My DataTemplate should display the collection "a" with a ComboBox and display the ith element of the collection "b" (6 courts double) corresponding to the selected item in the ComboBox.

Sorry for my english and if I was not clear enough.