how to use radcombobox

Question

below are my codes, working excellent but problem is ,whenever i select item from combobox it selects well but whenever i insert it insert only the first item i.e i have selected item no 2 and its primary key is 1 it will keep inserting the first item 

private void Load()

{

tsuppliertrans = SvcClient.GetSuppliertrans();

drvSupptrans.DataSource = tsuppliertrans;

drvSupptrans.DataBind();

tproducts = SvcClient.GetAccs();

rdcAccesoryid.DataSource = tproducts;

rdcAccesoryid.DataValueField = "acc_id";

rdcAccesoryid.DataTextField = "acc_description";

rdcAccesoryid.DataBind();

tsupplier = SvcClient.GetSuppliers();

rdsuppid.DataSource = tsupplier;

rdsuppid.DataValueField = "supplier_id";

rdsuppid.DataTextField = "supplier_name";

rdsuppid.DataBind();

}

protected void btnSubmit_Click(object sender, EventArgs e)

{

suppliertrans.product_id = Convert.ToInt32(rdcAccesoryid.SelectedValue);

suppliertrans.supplier_id = Convert.ToInt32(rdsuppid.SelectedValue.ToString());

suppliertrans.date_of_purchase = Convert.ToDateTime(rdtpDate.SelectedDate);

suppliertrans.Mode_of_payments = rdcmodeofpayment.SelectedValue.ToString();

suppliertrans.amount_paid = Convert.ToDecimal(tdtAmount.Text);

suppliertrans.balance = Convert.ToDecimal(rdtxtRuningbalance.Text);

suppliertrans = SvcClient.SetSuppliertrans(suppliertrans);

 

kindly help