C# ListView Appears Blank with Groups

You should not add items to the group, but rather adding items to the list view, and for each item set its Group property to the desired group.

You can see an example in this MSDN link

If items are added to the listview while the ShowGroups value is set to false and then the ShowGroups property is later set to true, the listbox will appear blank while showing groups (but with content when ShowGroups is false).

ShowGroups needs to be true when building the list.

The timing is also important. The listbox needs to be rendered before the ShowGroups property is set to false. I set it in my dialog shown event.

I discovered this while working in .Net 4.0.