使用反射的Wcf动态主机

Question

我的目标是创建一个能够解析多个程序集、检测契约和托管服务的宿主应用程序。

为了加载服务，我们通常需要对servicehost实例化进行硬编码。下面的代码虽然不是我想要的行为，但仍然可以正常工作。

ServiceHost wService1Host = new ServiceHost(typeof(Service1));
wService1Host.Open();

ServiceHost wService2Host = new ServiceHost(typeof(Service2));
wService2Host.Open();

然而，这意味着我提前知道了服务是什么。我不介意引用包含服务的程序集。我只希望宿主不知道程序集中包含了什么服务。例如，如果我向其中一个程序集添加一个新服务，则不需要在主机端进行任何更改。

这与这个question非常相似，但是由于上面提到的原因而增加了复杂性。

这是我到目前为止附带的主机代码。目前我并不介意管理这些服务，我只是希望它们能够正确加载。

class Program
  {
    static void Main(string[] args)
    {

      // find currently executing assembly
      Assembly curr = Assembly.GetExecutingAssembly();

      // get the directory where this app is running in
      string currentLocation = Path.GetDirectoryName(curr.Location);

      // find all assemblies inside that directory
      string[] assemblies = Directory.GetFiles(currentLocation, "*.dll");

      // enumerate over those assemblies
      foreach (string assemblyName in assemblies)
      {
        // load assembly just for inspection
        Assembly assemblyToInspect = Assembly.ReflectionOnlyLoadFrom(assemblyName);

        // I've hardcoded the name of the assembly containing the services only to ease debugging
        if (assemblyToInspect != null && assemblyToInspect.GetName().Name == "WcfServices")
        {
          // find all types
          Type[] types = assemblyToInspect.GetTypes();

          // enumerate types and determine if this assembly contains any types of interest
          // you could e.g. put a "marker" interface on those (service implementation)
          // types of interest, or you could use a specific naming convention (all types
          // like "SomeThingOrAnotherService" - ending in "Service" - are your services)
          // or some kind of a lookup table (e.g. the list of types you need to find from
          // parsing the app.config file)
          foreach (Type ty in types)
          {
            Assembly implementationAssembly = Assembly.GetAssembly(ty);
            // When loading the type for the service, load it from the implementing assembly.
            Type implementation = implementationAssembly.GetType(ty.FullName);

            ServiceHost wServiceHost = new ServiceHost(implementation); // FAIL
            wServiceHost.Open();
          }
        }
      }
      Console.WriteLine("Service are up and running.");
      Console.WriteLine("Press <Enter> to stop services...");
      Console.ReadLine();
    }
  }

尝试创建serviceHost时出现以下错误：

"It is illegal to reflect on the custom attributes of a Type loaded via ReflectionOnlyGetType (see Assembly.ReflectionOnly) -- use CustomAttributeData instead."

在上面给出的链接中，这个家伙似乎已经使用typeof解决了它的问题，因为他提前知道他想要公开什么服务。不幸的是，这不是我的案子。

注意:对于托管部分，我实际上有3个项目。第一个是主机应用程序(见上)，第二个是包含所有服务契约(接口)的程序集，最后一个程序集包含服务实现。

这是我实际用于托管服务的app.config。包含实现的程序集名为"WcfServices“，包含2个服务。一种是公开回调，另一种只公开基本服务。

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>    
    <behaviors>
      <serviceBehaviors>  
        <behavior name="metadataBehavior">
          <serviceMetadata httpGetEnabled="true"/>
        </behavior>        
      </serviceBehaviors>  
    </behaviors>
    <services>
      <service name="WcfServices.Service1"
               behaviorConfiguration="metadataBehavior">

        <endpoint address="Service1Service"
                  binding="basicHttpBinding"
                  contract="WcfServices.IService1"
                  name="basicHttp"/>

        <endpoint binding="mexHttpBinding"
                  contract="IMetadataExchange"
                  name="metadataExchange"/>

        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8000/Service1"/>
          </baseAddresses>
        </host>        
      </service>

      <service name="WcfServices.Service2"
               behaviorConfiguration="metadataBehavior">

        <endpoint address="Service2Service"
                  binding="wsDualHttpBinding"
                  contract="WcfServices.IService2"/>

        <endpoint address="mex"
                  binding="mexHttpBinding"
                  contract="IMetadataExchange"/>

        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8000/Service2"/>
          </baseAddresses>
        </host>
      </service>

    </services>    
  </system.serviceModel>
</configuration>

所以，需要明确的是，这是我要找的：

1. 在当前应用程序directory
2. Looks中加载程序集如果其中有任何协定实现
3. 如果有，则实例化这些服务(暂时使用app.config )

首先，这有可能吗？(我的猜测是，因为一个名为wcfstorm alread的应用程序似乎可以做到这一点)

显然，我怎样才能让上面的代码工作呢？

谢谢!

Answer 1

这就是我最终要做的：

private static void LoadServices()
{
  // find currently executing assembly
  Assembly Wcurr = Assembly.GetExecutingAssembly();

  // get the directory where this app is running in
  string wCurrentLocation = Path.GetDirectoryName(Wcurr.Location);

  // enumerate over those assemblies
  foreach (string wAssemblyName in mAssemblies)
  {
    // load assembly just for inspection
    Assembly wAssemblyToInspect = null;
    try
    {
      wAssemblyToInspect = Assembly.LoadFrom(wCurrentLocation + "\\" + wAssemblyName);
    }
    catch (System.Exception ex)
    {
      Console.WriteLine("Unable to load assembly : {0}", wAssemblyName);
    }


    if (wAssemblyToInspect != null)
    {
      // find all types with the HostService attribute
      IEnumerable<Type> wTypes = wAssemblyToInspect.GetTypes().Where(t => Attribute.IsDefined(t, typeof(HostService), false));

      foreach (Type wType in wTypes)
      {
        ServiceHost wServiceHost = new ServiceHost(wType);
        wServiceHost.Open();
        mServices.Add(wServiceHost);
        Console.WriteLine("New Service Hosted : {0}", wType.Name);
      }
    }
  }

  Console.WriteLine("Services are up and running.");
}

注意:这种方法要求程序集被“宿主”项目引用。

Note2 :为了加速程序集解析，我在"mAssemblies“中硬编码了哪些程序集要加载。