Datagrid results do not make sense

I've been working with the DataGrid in WPF with great results. However, it is now giving me unexpected results after some changes.

BEFORE: I had a DataGrid on a page. The DataContext was set to a L开发者_如何学运维ist object that was created from a class that existed within the same WPF project. The empty row at the bottom of the DataGrid, to add new records, is visible

AFTER: Same page, same DataGrid. But now the List object is coming from a Class Library project within the same solution. EXACT same code, but it's now been extracted into a class library. The empty row at the bottom of the datagrid, to add new records is not visible.

WTF?

I think I finally have the answer. Basically, I was mistaken, I did change a tiny portion of the class. The "lightbulb" went on when I read the answers to this one: How do I create a new row in WPF DataGrid when it is bound to an XmlDataProvider?

Bottom Line: The class you are binding to needs to have a default constructor in order to display an editable row!

In my code, I did change the constructors (I completely forgot about that) which left no default. Adding the default constructor back into the class fixed the problem.

Maybe it is some security issue or even a bug. I just read this:

I found that if you access the CanAddRow of ListCollectionView once before you use the collection, magically the CanUserAddRows of the DataGrid becomes true. Strange!

IEditableCollectionView ecv = new ListCollectionView(myRecordCache);
bool b = ecv.CanAddNew;   // dummy access
MyGrid.DataContext = ecv;

What kind of list is it? Does its publically visible interface allow to add items or is it a readonly list now (e.g. IEnumerable, ICollection?

I encountered the same problem when I set the DataGrid property IsReadOnly="True". Check if you have the same setting and try to remove it to see what happens.