Как вставить данные gridview в базу данных

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я получаю ошибку входная строка была не в правильном формате

Что я уже пробовал:

try
{
    if (ViewState["dtAck"] != null)
        dtAck = ViewState["dtAck"] as DataTable;

    if (dtAck == null)
        dtAck = AddPanchayats();
    string strFile = string.Empty;
    if (dtAck.Rows.Count > 0)
    {
        //Saving the data
        DataSet dataSetPanchayats = new DataSet();
        dataSetPanchayats.Tables.Add(dtAck);
        string fName = string.Empty;

        foreach (GridViewRow gvr in gvhouseholddetials.Rows)
        {
            TextBox i = (TextBox)gvr.FindControl("txtNOOFCARDSDISTRIBUTED");
            CheckBox checkBox = (CheckBox)gvr.FindControl("checkBox");
            int totalJC = Convert.ToInt32(gvhouseholddetials.Rows[gvr.RowIndex].Cells[4].Text.Trim());
            if (Convert.ToInt32(i.Text) > totalJC && checkBox.Checked)
            {
                ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Warning", "alert('Please enter proper value of Total no of cards distributed');", true);
                //gvhouseholddetials.Rows[gvr.RowIndex].Focus();
                TextBox txtNOOFCARDSDISTRIBUTED = gvhouseholddetials.Rows[gvr.RowIndex].FindControl("txtNOOFCARDSDISTRIBUTED") as TextBox;
                txtNOOFCARDSDISTRIBUTED.Focus();
                txtNOOFCARDSDISTRIBUTED.Enabled = true;
                checkBox.Checked = false;
                return;
            }

            TextBox d = (TextBox)gvr.FindControl("txtD");
            string txtdate = Convert.ToString(d.Text);

            if (txtdate == "")
            {
                ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Warning", "alert('Please select distributed date');", true);
                gvhouseholddetials.Rows[gvr.RowIndex].Focus();
                gvhouseholddetials.Rows[gvr.RowIndex].Cells[5].Focus();
                gvhouseholddetials.Rows[gvr.RowIndex].Cells[5].Enabled = true;

                TextBox txtTD = gvhouseholddetials.Rows[gvr.RowIndex].FindControl("txtD") as TextBox;
                txtTD.Enabled = true;
                checkBox.Checked = false;
                return;
            }
            if (txtdate != "" && checkBox.Checked)
            {
                DateTime myDate = DateTime.ParseExact(txtdate, "dd/MM/yyyy", System.Globalization.CultureInfo.InvariantCulture);
                DateTime startDate = DateTime.ParseExact("01/01/2017", "dd/MM/yyyy", System.Globalization.CultureInfo.InvariantCulture);
                if (myDate > DateTime.Today || myDate < startDate)
                {
                    ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Warning", "alert('Please enter proper date' );", true);
                    gvhouseholddetials.Rows[gvr.RowIndex].Focus();
                    gvhouseholddetials.Rows[gvr.RowIndex].Cells[5].Focus();
                    gvhouseholddetials.Rows[gvr.RowIndex].Cells[5].Enabled = true;

                    TextBox txtTD = gvhouseholddetials.Rows[gvr.RowIndex].FindControl("txtD") as TextBox;

                    txtTD.Enabled = true;
                    checkBox.Checked = false;
                    return;
                }
            }


        }


        string msg = new GenericBO().GetString(new object[] { dataSetPanchayats.GetXml(), objPortalUser.PCCInfoCode, objPortalUser.UserName, null }, "JobCard_Printing.SaveAcknowledgedJobCard_APO");
        if (msg == "SUCCESS")
        {
            ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Warning", "alert('Data saved successfully');", true);
            ViewState.Remove("dtAck");
            gvhouseholddetials.DataBind();
            ViewState.Remove("bindGrid");
            //btnSubmit.Visible = false;
        }

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