how to retrive data from gridview with multiple checkbox in c# for insert data in datatable

protected void Btnsave_Click(object sender, EventArgs e)
{
  try
  {
    //if (DDlStandard.SelectedValue !=null)
    //{
    nv.Clear();
    nv.Add("@Flag", "Insert");
    string TimeTableId = hlp.GetNextNoMax("TimeTblMstr", "TimeTblId", "TT", "3");
    nv.Add("@TimeTblId", TimeTableId);
    nv.Add("@StdId", DDlStandard.SelectedValue.ToString());
    nv.Add("@DivId", DDlDivision.SelectedValue.ToString());
    nv.Add("@SubjId", DDlSubj.SelectedValue.ToString());

    for ( int i = 0; i < GridView1.Rows.Count; i++ )
    {
      CheckBox chkMon = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chkMon");
      if ( chkMon.Checked )
      {
        nv.Add("@sessionId", GridView1.Rows[i].ToString());
        nv.Add("@Mon", "Y");
      }
      else
      {
        nv.Add("@Mon", "N");
      }
      CheckBox chkTue = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chkTue");
      if ( chkTue.Checked )
      {
        nv.Add("@sessionId", GridView1.Rows[0].ToString());
        nv.Add("@Tue", "Y");
      }
      else
      {
        nv.Add("@Tue", "N");
      }
      CheckBox chkWed = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chkWed");
      if ( chkWed.Checked )
      {
      }
      CheckBox chkThu = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chkThu");
      if ( chkThu.Checked )
      {
      }
      CheckBox chkFri = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chkFri");
      if ( chkFri.Checked )
      {
      }
      CheckBox chkTue = (CheckBox)GridView1.Rows[i].Cells[0].FindControl("chk");
      if ( chkTue.Checked )
      {
      }
    }
    int ans = Convert.ToInt32(hlp.Insert("[SPTimeTbl]", nv));
    if ( ans == 1 )
    {
      ScriptManager.RegisterStartupScript(this, typeof(Page), UniqueID, "alert('Successfully Submitted');", true);
    }
    else
    {
      ScriptManager.RegisterStartupScript(this, typeof(Page), UniqueID, "alert('Problem In Submitting...Try Again');", true);
    }

  }
  catch
  {
  }

}