private void ShowVendors()
{
SupplierTransaction vendor = new SupplierTransaction();
DataTable dtOneTimeSuppliers = vendor.GetOneTimeSuppliers(connstring, hdnCategoryId.Value.Trim());
ddlVendorName.DataSource = dtOneTimeSuppliers;
ddlVendorName.DataTextField = "VendorName";
ddlVendorName.DataValueField = "VendorId";
ddlVendorName.DataBind();
ddlVendorName.Items.Insert(0, "");
}