Use following Function to get Column Index:
private int GetColumnIndexByName(GridView grid, string name) { foreach (DataControlField col in grid.Columns) { if (col.HeaderText.ToLower().Trim() == name.ToLower().Trim()) { return grid.Columns.IndexOf(col); } } return -1; }

I figured it out, I needed to be using `DataControlField` and slightly different syntax.
The working version:
private int GetColumnIndexByName(GridView grid, string name) { foreach (DataControlField col in grid.Columns) { if (col.HeaderText.ToLower().Trim() == name.ToLower().Trim()) { return grid.Columns.IndexOf(col); } } return -1; }