Items collection must be empty before using ItemSource using custom list

Question

In my class ResultEntity if I do:

_resultMulti = new List(); 

I see the following error message:

Answer 1

Just wrap your column definitions with DataGrid.Columns. As you are binding it using ItemsSource you can't put any direct content in the definition. It is considering your columns as items of the grid which can't go with ItemsSource collection.