How to insert datagridview into SQL database after reading it from excel

My datagridview:

      Date    |    EmployeeID1  |   EmployeeID2  |  EmployeeID3
---------------------------------------------------------------------
 18/1/2018            1                          2                       3
 19/1/2018            2                          3                       1
 20/1/2018            1                          2                       3



How I want it to be like in my SQL Database:
DutyID        |       Date      |          EmployeeID       |      Shift
------------------------------------------------------------------------------------
       1               18/1/2018	       EmployeeID1                1
       2               18/1/2018               EmployeeID2                2
       3               18/1/2018               EmployeeID3                3
       4               19/1/2018               EmployeeID1                2
       5               19/1/2018               EmployeeID2                3
       6               19/1/2018               EmployeeID3                1
       7               20/1/2018               EmployeeID1                1
       8               20/1/2018               EmployeeID2                2
       9               20/1/2018               EmployeeID3                3

private void btnInsert_Click(object sender, EventArgs e)
        {

                for (int r = 1; r < dataGridView1.Rows.Count; r++)
                {
                    for (int c = 1; c < dataGridView1.Columns.Count; c++)
                    {
                        try
                        {
                            SqlConnection con = new SqlConnection(constring);
                            SqlCommand query = new SqlCommand("INSERT into RosterTest (EmployeeID, Date, ShiftType) Values (@EmployeeID,@Date,@ShiftType", con);
                            query.Parameters.Add("@EmployeeID", SqlDbType.Int).Value = dataGridView1.Columns[c].HeaderText;
                            query.Parameters.Add("@Date", SqlDbType.Date).Value = dataGridView1.Rows[r].Cells;
                            con.Open();
                            query.ExecuteNonQuery();

                           

                        }
                        catch (Exception ex)
                        {
                            MessageBox.Show(ex.Message);
                        }
                    }
                }