ช่วยหน่อย!! ติดปัญหา Select from where แต่ข้อมูลไม่มาลองมา 2-3 วิธีไม่ได้ผล พอจะมีวิธีไหนอีกบ้างไหมครับ

            SqlConnection con = new SqlConnection("Data Source=(local)\\SQLEXPRESS;Initial Catalog=DBTest;Integrated Security=SSPI");
            con.Open();
            string serviceid = txtDate.Text = "00001";
            //string strdatetime = txtDate.Text;
            SqlDataAdapter da = new SqlDataAdapter("select * from tblJoin where ServiceReqID = '@serviceid'", con);        
            DataTable dt = new DataTable();
            da.Fill(dt);
            dataGridView1.DataSource = dt;

SqlDataAdapter da = new SqlDataAdapter("select * from tblJoin where ServiceReqID = 'serviceid'", con

SqlDataAdapter da = new SqlDataAdapter("select * from tblJoin where ServiceReqID = serviceid ", con

SqlDataAdapter da = new SqlDataAdapter("select * from tblJoin where ServiceReqID = '00001'", con);