sending null values from datetimepicker to the database

Question

hi can someone please help me with this issue? i want to send a null value to the database from datetimepicker but it doesnt work, it doesnt give an error but everytime i uncheck the checbox near on the datetimepicker the date still enters :( can anyone please help with this

    private void BtnSave_Click(object sender, EventArgs e)
    {

        using (SqlConnection sqlConn = new SqlConnection("Data Source=TANYA-PC;Initial Catalog=biore1;Integrated Security=True"))
        {
            string sqlQuery = @"INSERT INTO cottonpurchase VALUES(@slipNo, @purchasedate, @farmercode, @farmername, @villagename, @basicprice, @weight, @totalamountbasic, @premium, @totalamountpremium, @totalamountpaid,  @certstatus)";



            using (SqlCommand cmd = new SqlCommand(sqlQuery, sqlConn))
            {
                cmd.Parameters.Add("@slipNo", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtSlipNo.Text)) ? int.Parse(TxtSlipNo.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@purchasedate", SqlDbType.DateTime).Value = Date.Text;
                if (Date.Checked)
                    cmd.Parameters.AddWithValue("purchdate", Date);
                else
                    cmd.Parameters.AddWithValue("purchdate", DBNull.Value);
                 cmd.Parameters.Add("@farmercode", SqlDbType.Int).Value = TxtFarmerCode.Text;

                cmd.Parameters.Add("@farmername", SqlDbType.VarChar, 100).Value = TxtFarmerName.Text;
                cmd.Parameters.Add("@villagename", SqlDbType.VarChar, 100).Value = TxtVillageName.Text;
                cmd.Parameters.Add("@basicprice", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtBasicPrice.Text)) ? int.Parse(TxtBasicPrice.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@weight", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtWeight.Text)) ? int.Parse(TxtWeight.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@totalamountbasic", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtTotalAmountBasic.Text)) ? int.Parse(TxtTotalAmountBasic.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@premium", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtPremium.Text)) ? int.Parse(TxtPremium.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@totalamountpremium", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtTotalAmountPremium.Text)) ? int.Parse(TxtTotalAmountPremium.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@totalamountpaid", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtTotalAmountPaid.Text)) ? int.Parse(TxtTotalAmountPaid.Text) : (object)DBNull.Value;
                //d.Parameters.Add("@yeildestimates", SqlDbType.Int).Value = (!String.IsNullOrEmpty(TxtYeildEstimates.Text)) ? int.Parse(TxtYeildEstimates.Text) : (object)DBNull.Value;
                cmd.Parameters.Add("@certstatus", SqlDbType.VarChar, 100).Value = comboBox1.Text;
                sqlConn.Open();

Answer 1

It doesn't look like parameter purchdate is used anywhere.

Maybe try something like this:

   //cmd.Parameters.Add("@purchasedate", SqlDbType.DateTime).Value = Date.Text;
   if (Date.Checked)
        cmd.Parameters.AddWithValue("@purchasedate", Date);
   else
        cmd.Parameters.AddWithValue("@purchasedate", DBNull.Value);

Answer 2

Doesn't it have anything to do with the following lines?

cmd.Parameters.Add("@purchasedate", SqlDbType.DateTime).Value = Date.Text;
if (Date.Checked)
    cmd.Parameters.AddWithValue("purchdate", Date);
else
    cmd.Parameters.AddWithValue("purchdate", DBNull.Value);

You are setting the @purchasedate param outside the if, so it's always setted.

If this is not the problem, you should post the UI code, for us to have some more info to answer.