protected void BtnQuery_Click(object sender, EventArgs e)
{
string orderDateFilterValue = ddlOrderDate.SelectedValue == "" ? "Last 6 Months" : ddlOrderDate.SelectedValue;
string customerId = txtBoxCustomerID.Text == "" ? null : txtBoxCustomerID.Text;
string custName = txtBoxUserName.Text == "" ? null : txtBoxUserName.Text;
string salesMgr = ddlSalesManager.SelectedValue == "" ? null : ddlSalesManager.SelectedValue;
OrdersDAL orders = new OrdersDAL();
DataSet ds = orders.GetOrdersWithFilterOptions(orderDateFilterValue, customerId, custName, salesMgr);
gvOrders.DataSource = ds;
gvOrders.DataBind();
}