conn = new SqlConnection(ProjectConnection.ConnectionString);
            SqlCommand comm2 = new SqlCommand();
            comm2.Connection = conn;
            comm2.CommandText = "UPDATE Duty SET Edit=@Edit  WHERE Current_project='" + Projects_list.SelectedValue + "' AND Date >= "+ Calendar1.SelectedDate+" AND Date <= "+ Calendar2.SelectedDate ;
            conn.Open();

            comm2.Parameters.AddWithValue("@Edit", "1");
            comm2.ExecuteNonQuery();
            conn.Close();