แนะนำวิธีตรวจสอบรหัสพนักงานเพื่อนเข้าหน้าตามสิทธิผู้ใช้ ASP.NET C# หน่อยค่ะ

{
         String strConnString;
         strConnString = "Server=localhost;UID=sa;PASSWORD=12345;database=mydatabase";
         objConn = new System.Data.SqlClient.SqlConnection(strConnString);
         objConn.Open();

         String strSQL;
         strSQL = " SELECT  * FROM Register WHERE UserName = '" + this.txtUsername.Text + "' AND [Password] = '" + this.txtPass.Text + "' ";
         dtAdapter = new System.Data.SqlClient.SqlDataAdapter(strSQL, objConn);
         dtAdapter.Fill(dt);

         if (dt.Rows.Count > 0)
         {
             Session["strUserID"] = dt.Rows[0]["UserID"].ToString();
             Session["strUser"] = this.txtUsername.Text;
             if (Session["Status"] == "ADMIN")
             {
                 Response.Redirect("ADMIN.aspx");
             }
             else 
             {
                  Response.Redirect("USER.aspx");
             }

         }
         else
         {
             this.lblStatus.Visible = true;
             this.lblStatus.Text = "กรุณาตรวจสอบ Username&Password!!";
         }

         dtAdapter = null;
         objConn.Close();
         objConn = null;
     }