C# 訊息佇列應用程式開發：XML 配置與中繼資料架構（三）

配置存取：ConfigManager 與中繼資料

應用程式運行時配置透過 System.Configuration.ConfigManager 讀取 XML 配置檔。靜態 Get 方法回傳集合，列舉取得單一屬性。除主配置檔外，需建立中繼資料結構定義檔（.xms），並在伺服器 Machine.config 註冊：

<?xml version="1.0"?>
<MetaData xmlns="x-schema:CatMeta.xms">
  <DatabaseMeta InternalName="MessageService">
    <ServerWiring Interceptor="Core_XMLInterceptor"/>
    <Collection InternalName="Process" PublicName="ProcessList" PublicRowName="ProcessDefinition" SchemaGeneratorFlags="EMITXMLSCHEMA">
      <Property InternalName="ProcessName" Type="String" MetaFlags="PRIMARYKEY"/>
      <Property InternalName="ProcessDesc" Type="String"/>
      <Property InternalName="ProcessType" Type="Int32" DefaultValue="RoundRobin">
        <Enum InternalName="RoundRobin" Value="0"/>
        <Enum InternalName="AppSpecific" Value="1"/>
        <Enum InternalName="Assembly" Value="2"/>
      </Property>
      <Property InternalName="ProcessThreads" Type="Int32" DefaultValue="1"/>
      <Property InternalName="InputQueue" Type="String"/>
      <Property InternalName="ErrorQueue" Type="String"/>
      <Property InternalName="OutputName" Type="String"/>
      <QueryMeta InternalName="All" MetaFlags="ALL"/>
      <QueryMeta InternalName="QueryByFile" CellName="__FILE" Operator="EQUAL"/>
    </Collection>
    <Collection InternalName="Output" PublicName="OutputList" PublicRowName="OutputDefinition" SchemaGeneratorFlags="EMITXMLSCHEMA">
      <Property InternalName="ProcessName" Type="String" MetaFlags="PRIMARYKEY"/>
      <Property InternalName="OutputName" Type="String" MetaFlags="PRIMARYKEY"/>
      <QueryMeta InternalName="All" MetaFlags="ALL"/>
      <QueryMeta InternalName="QueryByFile" CellName="__FILE" Operator="EQUAL"/>
    </Collection>
    <RelationMeta PrimaryTable="Process" PrimaryColumns="ProcessName" ForeignTable="Output" ForeignColumns="ProcessName" MetaFlags="USECONTAINMENT"/>
  </DatabaseMeta>
</MetaData>

服務啟動：載入配置建立 Worker

private Hashtable htWorkers = new Hashtable();
IConfigCollection cWorkers = ConfigManager.Get("ProcessList", new AppDomainSelector());
foreach (IConfigItem ciWorker in cWorkers) {
  WorkerFormatter sf = new WorkerFormatter();
  sf.ProcessName = (string)ciWorker["ProcessName"];
  sf.ProcessDesc = (string)ciWorker["ProcessDesc"];
  sf.NumberThreads = (int)ciWorker["ProcessThreads"];
  sf.InputQueue = (string)ciWorker["InputQueue"];
  sf.ErrorQueue = (string)ciWorker["ErrorQueue"];

  switch ((int)ciWorker["ProcessType"]) {
    case 0: sf.ProcessType = WorkerFormatter.SFProcessType.ProcessRoundRobin; break;
    case 1: sf.ProcessType = WorkerFormatter.SFProcessType.ProcessAppSpecific; break;
    case 2: sf.ProcessType = WorkerFormatter.SFProcessType.ProcessAssembly; break;
    default: throw new Exception("Unknown Processing Type");
  }

  string procName = (string)ciWorker["ProcessName"];
  if (htWorkers.ContainsKey(procName))
    throw new ArgumentException("Process Name Must be Unique: " + procName);
  htWorkers.Add(procName, new CWorker(sf));
}

Hashtable 以 ProcessName 為鍵，支援快速查找與列舉。WorkerFormatter 結構體封裝運行時參數（值型別，避免參考語意副作用）。