Error แบบนี้ค่ะ มีใครรู้บ้างค่ะควรแก้ยังไง The variable name '@Ts' has already been declared. Variable names must be unique within a query batch or stored procedure.

    protected void btnAssignsubmit_Click(object sender, EventArgs e)
    {
        DateTime Ts = Convert.ToDateTime(txtAssignDate.Text + " " + txtAssignTime.Text);
        txt4.Text = txtAssignDate.Text + " " + txtAssignTime.Text;

        for (int i = 0; i <= grdAssignList.Rows.Count - 1; i++)
        {
            CheckBox chkDel = (CheckBox)grdAssignList.Rows[i].FindControl("chkAssignList");
            Label lblID = (Label)grdAssignList.Rows[i].FindControl("lblALisid");

            if (chkDel.Checked)
            {
                con.Open();
                String sqlSelect8 = "select Listtime3 from Listhealty where ListId = '" + lblID.Text + "'";
                com.CommandText = sqlSelect8;
                com.Connection = con;

                SqlDataReader dr;
                dr = com.ExecuteReader();
                dr.Read();

                txt3.Text = dr["Listtime3"].ToString();

                int Time = Convert.ToInt32(txt3.Text);
                DateTime TimeS = Convert.ToDateTime(txt4.Text);
                DateTime Result = TimeS.AddMinutes(Time);

                switch (i)
                {
                    case 1:
                        // จะทำอะไร ก้อใส่สะตรงนี้ค่ะ
                        break;
                }
                con.Close();

                String sqlInsert = "insert into Assign(ClinicId, StaffId, ListId, PatientId, AssignDate, AssignTimestart, Timestart, Timefinish, Assigndetail) " + "values('" + Session["sessionAssCli"] + "', '" + Session["sessionAssSta"] + "', '" + lblID.Text + "','"
                    + Session["sessionPatientId"] + "', '" + txtAssignDate.Text + "','" + txtAssignTime.Text + "', @Ts, @re, '" + txtAssigndetail.Text + "')";


                com.CommandText = sqlInsert;
                com.Connection = con;

                com.Parameters.Add("@Ts", SqlDbType.DateTime).Value = Ts;
                com.Parameters.Add("@re", SqlDbType.DateTime).Value = Result;

                con.Open();
                com.ExecuteNonQuery();
                com.Parameters.Clear();
                con.Close();
            }
        }
    }
}