c# - 类型初始化异常 : The type initializer for 'vService.CheckService' threw an exception

Question

我在调用 WCF 服务时收到如下 FaultException:

2012-04-02 16:26:00.3593|Error|System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]: The type initializer for 'vService.CheckService' threw an exception. (Fault Detail is equal to An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is:
System.TypeInitializationException: The type initializer for 'vService.CheckService' threw an exception. ----> System.NullReferenceException: Object reference not set to an instance of an object.
   at vService.CheckService..cctor() in d:\working\code\VioletServer\vService\CheckService.cs:line 14
   --- End of inner ExceptionDetail stack trace ---
   at vService.CheckService..ctor()
   at CreatevService.CheckService()
   at System.ServiceModel.Dispatcher.InstanceProvider.GetInstance(InstanceContext instanceContext, Message message)
   at System.ServiceModel.Dispatcher.InstanceBehavior.GetInstance(InstanceContext instanceContext, Message request)
   at System.ServiceModel.InstanceContext.GetServiceInstance(Message message)
   at System.ServiceModel.Dispatcher.InstanceBehavior.EnsureServiceInstance(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc& rpc)
  ...).

CheckService.cs的第14行是

private static string connStr = ConfigurationManager.ConnectionStrings["violetdb"].ConnectionString;

异常在这种情况下意味着什么，我该如何解决？

---

//CheckService.cs
public class CheckService : ICheckService
{
    private static string connStr = ConfigurationManager.ConnectionStrings["violetdb"].ConnectionString;
    MessageRepository _repo = new MessageRepository(connStr);

    public CheckService(){}

    public CheckService(MessageRepository repo)
    {
        _repo = repo;
    }

    public void SendMessage(string sender, string recipient, string messagetext)
    {
        _repo.DeliverMessage(sender,recipient,messagetext);
    }
}

Answer 1

您的 WCF 服务很可能在其应用程序配置文件中没有名为“violetdb”的连接字符串。

A TypeInitializerException在这种情况下被抛出，因为你有一个 static在类型构造之前初始化的字段，因为 ConnectionStrings["violetdb"]电话正在返回 null , 它正在抛出 NullReferenceException .

底线，检查 <connectionStrings>配置文件的一部分并确保连接字符串存在。