C# WPF Gridview does not show some columns values

Hi 

one of my gridviews has more than 50 columns. when I use DtGrResult.ItemsSource = tbl_main; it shows all values but when I'm using DtGrResult.ItemsSource = tbl_main.AsDataView(); the columns from 29 till end don't have any value. How can I solve this problem?

Thank you