使用CustomConfigurationSource创建NServiceBus时出现异常

我需要使用CustomConfigurationSource创建一个NServiceBus来替换我的app.config .

我在我的代码中实现了CustomConfiguration源，但是在创建总线时出现以下异常：

System.NullReferenceException未处理HResult = -2147467261 Message =对象引用未设置为对象的实例 . Source = NServiceBus.Core StackTrace：位于c：\ TeamCity \ buildAgent \ work \ nsb.master_10 \ src \ unicast \ NServiceBus.Unicast \ UnicastBus.cs中的NServiceBus.Unicast.UnicastBus.NServiceBus.IStartableBus.Start（Action startupAction）：line 852

我在A班创建我的公共汽车如下：

public class A: IA
{
    public static IBus Bus { get; private set; }

    public A()
    {
        CreateBus();
    }

    private void CreateBus()
    {
        Bus = NServiceBus.Configure.With()
            .CustomConfigurationSource(new AConfigSource())
            .Log4Net()
            .DefaultBuilder()
            .XmlSerializer()
            .MsmqTransport()
                .IsTransactional(false)
                .PurgeOnStartup(false)
            .UnicastBus()
                .LoadMessageHandlers()
                .ImpersonateSender(false)
            .CreateBus()
            .Start(() => Configure.Instance.ForInstallationOn<NServiceBus.Installation.Environments.Windows>().Install());
            // Exception thrown here ******
    }
}

我的配置类：

public class AConfigSource: IConfigurationSource
{
    #region Implementation of IConfigurationSource

    public T GetConfiguration<T>() where T : class, new()
    {
        if (typeof(T) == typeof(MessageForwardingInCaseOfFaultConfig))
            return MessageForwardingInCaseOfFaultConfiguration() as T;

        if (typeof(T) == typeof(MsmqTransportConfig))
            return MsmqTransportConfiguration() as T;

        if (typeof(T) == typeof(UnicastBusConfig))
            return UnicastBusConfiguration() as T;

        // leaving the rest of the configuration as is:
        return ConfigurationManager.GetSection(typeof(T).Name) as T;

    }

    #endregion Implementation of IConfigurationSource

    #region Private

    private MessageForwardingInCaseOfFaultConfig MessageForwardingInCaseOfFaultConfiguration()
    {
        return new MessageForwardingInCaseOfFaultConfig
        {
            ErrorQueue = "error"
        };
    }

    private UnicastBusConfig UnicastBusConfiguration()
    {
        return new UnicastBusConfig();
    }

    private MsmqTransportConfig MsmqTransportConfiguration()
    {
        return new MsmqTransportConfig
        {
            ErrorQueue = "error",
            InputQueue = "myInputQueue",
            MaxRetries = 5,
            NumberOfWorkerThreads = 1
        };
    }

    #endregion Private
}

什么原因导致NullReferenceException？我错过了哪些步骤来覆盖我的所有nservicebus配置？

更新：我使用NServiceBus版本3.3.8 .

更新：根据John的回答，我更改了我的私有UnicastBusConfiguration方法，如下所示：

private UnicastBusConfig UnicastBusConfiguration()
    {
        return new UnicastBusConfig
        {
            ForwardReceivedMessagesTo = "",
            MessageEndpointMappings = new MessageEndpointMappingCollection()
        };
    }

我仍然得到上面提到的相同的例外 .

这是我需要在A类中运行的配置：

<configuration>
  <configSections>
    <section name="MsmqTransportConfig" type="NServiceBus.Config.MsmqTransportConfig, NServiceBus.Core" />
    <section name="UnicastBusConfig" type="NServiceBus.Config.UnicastBusConfig, NServiceBus.Core" />
    <section name="MessageForwardingInCaseOfFaultConfig" type="NServiceBus.Config.MessageForwardingInCaseOfFaultConfig, NServiceBus.Core" />
  </configSections>
  <MsmqTransportConfig ErrorQueue="error" NumberOfWorkerThreads="1" MaxRetries="5" />
  <UnicastBusConfig ForwardReceivedMessagesTo="">
    <MessageEndpointMappings></MessageEndpointMappings>
  </UnicastBusConfig>
  <MessageForwardingInCaseOfFaultConfig ErrorQueue="error" />
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="NServiceBus" publicKeyToken="9fc386479f8a226c" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.3.0.0" newVersion="3.3.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="NServiceBus.Core" publicKeyToken="9fc386479f8a226c" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.3.0.0" newVersion="3.3.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

更多信息：我正在运行WPF应用程序 . 我在我的解决方案中添加了一个类库来托管nservicebus . 我创建了一个上面提到的对象“A类”的实例 . 我需要nservicebus来配置基于app.config的A类，而不是我的WPF启动项目的app.config .

也许CustomConfigurationSource有点矫枉过正？有没有更好的方法来命令NServiceBus在A类项目中使用app.config进行配置？

更新：我收到以下错误，表示缺少UnicastBus.cs类 . 我在我的项目中引用了NserviceBus.Host ...

找到'c：\ TeamCity \ buildAgent \ work \ nsb.master_10 \ src \ unicast \ NServiceBus.Unicast \ UnicastBus.cs'的源代码 . （无校验和 . ）文件'c：\ TeamCity \ buildAgent \ work \ nsb.master_10 \ src \ unicast \ NServiceBus.Unicast \ UnicastBus.cs'不存在 . 查看'c：\ TeamCity \ buildAgent \ work \ nsb.master_10 \ src \ unicast \ NServiceBus.Unicast \ UnicastBus.cs'的脚本文档...查看'c：\ TeamCity \ buildAgent \ work \ nsb的项目.master_10 \ SRC \单播\ NServiceBus.Unicast \ UnicastBus.cs' . 在项目中找不到该文件 .