How to modify datarow itemarray value with example code

The below example give a clear explanation on How to modify a datarow in C#.

          SqlConnection con = new SqlConnection(connectionstring);

            string query = "Select * from App_Branch";

            con.Open();

            SqlCommand cmd = new SqlCommand(query, con);

            SqlDataAdapter da = new SqlDataAdapter(cmd);

            DataSet DS = new DataSet();

            da.Fill(DS);

            DataTable dt = new DataTable();

            foreach (DataRow item in DS.Tables[0].Rows)

            {

                if (item.ItemArray[2].ToString().Equals("0"))

                {

                    item["ColumnName"] = "Somthing";

//you can not give like this  item.ItemArray[4] = "Somthing";

                }

                else

                {

                    item["ColumnName"] = "Somthing";

                }

                dt.Rows.Add(item.ItemArray);

            }