รบกวนขอคำแนะนำหน่อย ORA-01745: invalid host/bind variable name (C# + Oracle)

        protected void ViewData()
        {
            //*** DataTable ***'
            OracleDataAdapter dtAdapter = default(OracleDataAdapter);
            DataTable dt = new DataTable();
            strSQL = "SELECT * FROM files WHERE FilesID = :sFilesID ";
            dtAdapter = new OracleDataAdapter(strSQL, objConn);
            objCmd = dtAdapter.SelectCommand;
            objCmd.Parameters.Add(":sFilesID", OracleType.Int32).Value = Request.QueryString["FilesID"];
            dtAdapter.Fill(dt);

            if (dt.Rows.Count > 0)
            {
                this.ImgPic.ImageUrl = "ViewImg.aspx?FilesID=" + dt.Rows[0]["FilesID"];
                this.txtName.Text = dt.Rows[0]["Name"].ToString();
            }

            dt = null;
        }

                DAL dal = new DAL();
                string myuser = this.login_name.Text.Trim().ToUpper();
                string mypass = this.login_pass.Text.Trim().ToUpper();
                string strSQL = "select username from tbluser where upper(username) = :myuser and upper(password) = :mypass ";
                List<OracleParameter> lstPara = new List<OracleParameter>();
                OracleParameter user = new OracleParameter();
                user.OracleDbType = OracleDbType.Varchar2;
                user.ParameterName = ":myuser";
                user.Value = myuser;
                lstPara.Add(user);
                OracleParameter pass = new OracleParameter();
                pass.OracleDbType = OracleDbType.Varchar2;
                pass.ParameterName = ":mypass";
                pass.Value = mypass;
                lstPara.Add(pass);
                string data = dal.executeScalar(strSQL,lstPara);

    public string executeScalar(string spName, List<OracleParameter> parameters)
    {
        string result = string.Empty;
        try
        {
            using (OracleConnection conn = new OracleConnection(strconn))
            {
                conn.Open();
                OracleDataAdapter dtAdapter = default(OracleDataAdapter);
                DataTable dt = new DataTable();
                OracleCommand cmd = new OracleCommand();
                dtAdapter = new OracleDataAdapter(spName, conn);
                cmd = dtAdapter.SelectCommand;
                if (parameters != null && parameters.Count > 0)
                {
                    // cmd.Parameters.AddRange(parameters);
                    foreach (OracleParameter item in parameters)
                    {
                        cmd.Parameters.Add(item);
                    }
                }
                dtAdapter.Fill(dt);

                if (dt.Rows.Count > 0)
                {
                    result = dt.Rows[0][0].ToString();
                }

                dt = null;
              
            }
            return result;
        }
        catch (OracleException ex)
        {
            throw new Exception("Error SQL " + ex);
        }
    }