Cannot apply indexing with [] to an expression of type 'ISet<string>'
问题 I am getting Error 'Cannot apply indexing with [] to an expression of type 'ISet'' for this code snippet foreach (GridViewRow grv in customTableDataList.UniGrid.GridView.Rows) { if (grv != null) { if (null != grv.FindControl(ItemCheckBoxID) && ((CheckBox)grv.FindControl(ItemCheckBoxID)).Checked) { //At this line I am getting error. itemIds += customTableDataList.UniGrid.ActionsID[rowCounter] + ", "; } rowCounter++; } } Can anyone give some more details to resolve this. 回答1: Add new using: