asp.net - 作为 Windows 服务托管的 c# WCF Restful Web 服务的跨源资源共享

Question

我有一个 WCF Restful 服务，我将其作为 Windows 服务托管。我想为我的服务添加跨域支持。但是，当我使用 global.asax 文件时，我可以轻松地做到这一点。但我想将我的服务托管为 Windows 服务。

我创建了一个项目，将我的服务作为 Windows 服务托管。现在我面临的问题是，我现在无法添加跨域支持。我尝试了通过 app.config 文件找到的所有可能的解决方案，但没有一个有效。我已经尝试过这些链接上的解决方案:

dotnet tricks

enable-cors.org

我尝试通过在每个服务契约(Contract)方法中调用以下函数来设置代码中的 header 。

private static void SetResponseHeader()
{
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Origin", "*");
WebOperationContext.Current.OutgoingResponse.Headers.Add("Cache-Control", "no-cache, no-store");
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Request-Methods", "GET, POST, PUT, DELETE, OPTIONS");
WebOperationContext.Current.OutgoingResponse.Headers.Add("Access-Control-Allow-Headers", "Content-Type, Accept");
}

界面:

namespace ReaderService
{
[ServiceContract]
public interface INFCReader
{
    [OperationContract]
    [WebInvoke(UriTemplate = "GetLogin", Method = "POST")]
    GetLoginResults GetLogin(DisplayRequest dispRequest);
}

这里 DisplayRequest 是一个类。

请大家帮忙。如果有人想查看任何其他代码，请告诉我。

非常感谢。

编辑:::::::

非常感谢托马斯的回复。我创建了一个实现 IDispatchMessageInspector 的 MessageInspector 类。我在 MessageInspector 类中有以下代码。

public class MessageInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", "*");
        if (HttpContext.Current.Request.HttpMethod == "OPTIONS")
        {
            HttpContext.Current.Response.AddHeader("Cache-Control", "no-cache");
            HttpContext.Current.Response.AddHeader("Access-Control-Allow-Methods", "GET, POST");
            HttpContext.Current.Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Accept");
            HttpContext.Current.Response.AddHeader("Access-Control-Max-Age", "1728000");
            HttpContext.Current.Response.End();
        }
        return null;
    }
}

我现在收到的错误是——“对象引用未设置为对象的实例。”错误就在上面代码的这一行

HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", "*");

我想做的就是向我的网络服务添加 CORS 支持。如果我做得正确，请告诉我。或者有没有其他方法可以做到同样的事情。

Answer 1

终于找到了解决我的疑问的方法。

一切都在这里。 Supporting Cross Origin Resource

很好的逐步解释。我想我自己永远无法解决这个问题。

代码:

创建 2 个类，如下所示:

1. MessageInspector 实现 IDispatchMessageInspector。
2. BehaviorAttribute 实现 Attribute、IEndpointBehavior 和 IOperationBehavior。

包含以下详细信息:

//MessageInspector Class
using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Description;
namespace myCorsService
{
  public class MessageInspector  : IDispatchMessageInspector
  {
    private ServiceEndpoint _serviceEndpoint;

    public MessageInspector(ServiceEndpoint serviceEndpoint)
    {
      _serviceEndpoint = serviceEndpoint;
    }

    /// <summary>
    /// Called when an inbound message been received
    /// </summary>
    /// <param name="request">The request message.</param>
    /// <param name="channel">The incoming channel.</param>
    /// <param name="instanceContext">The current service instance.</param>
    /// <returns>
    /// The object used to correlate stateMsg. 
    /// This object is passed back in the method.
    /// </returns>
    public object AfterReceiveRequest(ref Message request, 
                                          IClientChannel channel, 
                                          InstanceContext instanceContext)
    {
      StateMessage stateMsg = null;
      HttpRequestMessageProperty requestProperty = null;
      if (request.Properties.ContainsKey(HttpRequestMessageProperty.Name))
      {
        requestProperty = request.Properties[HttpRequestMessageProperty.Name]
                          as HttpRequestMessageProperty;
      }

      if (requestProperty != null)
      {
        var origin = requestProperty.Headers["Origin"];
        if (!string.IsNullOrEmpty(origin))
        {
          stateMsg = new StateMessage();
          // if a cors options request (preflight) is detected, 
          // we create our own reply message and don't invoke any 
          // operation at all.
          if (requestProperty.Method == "OPTIONS")
          {
            stateMsg.Message = Message.CreateMessage(request.Version, null);
          }
          request.Properties.Add("CrossOriginResourceSharingState", stateMsg);
        }
      }

      return stateMsg;
    }

    /// <summary>
    /// Called after the operation has returned but before the reply message
    /// is sent.
    /// </summary>
    /// <param name="reply">The reply message. This value is null if the 
    /// operation is one way.</param>
    /// <param name="correlationState">The correlation object returned from
    ///  the method.</param>
    public void BeforeSendReply(ref  Message reply, object correlationState)
    {
      var stateMsg = correlationState as StateMessage;

      if (stateMsg != null)
      {
        if (stateMsg.Message != null)
        {
          reply = stateMsg.Message;
        }

        HttpResponseMessageProperty responseProperty = null;

        if (reply.Properties.ContainsKey(HttpResponseMessageProperty.Name))
        {
          responseProperty = reply.Properties[HttpResponseMessageProperty.Name]
                             as HttpResponseMessageProperty;
        }

        if (responseProperty == null)
        {
          responseProperty = new HttpResponseMessageProperty();
          reply.Properties.Add(HttpResponseMessageProperty.Name,
                               responseProperty);
        }

        // Access-Control-Allow-Origin should be added for all cors responses
        responseProperty.Headers.Set("Access-Control-Allow-Origin", "*");

        if (stateMsg.Message != null)
        {
          // the following headers should only be added for OPTIONS requests
          responseProperty.Headers.Set("Access-Control-Allow-Methods",
                                       "POST, OPTIONS, GET");
          responseProperty.Headers.Set("Access-Control-Allow-Headers",
                    "Content-Type, Accept, Authorization, x-requested-with");
        }
      }
    }
  }

  class StateMessage
  {
    public Message Message;
  }
}

//BehaviorAttribute Class
using System;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;

namespace OpenBetRetail.NFCReaderService
{
  public class BehaviorAttribute : Attribute, IEndpointBehavior,
                                 IOperationBehavior
  {        
    public void Validate(ServiceEndpoint endpoint) { }

    public void AddBindingParameters(ServiceEndpoint endpoint,
                             BindingParameterCollection bindingParameters) { }

    /// <summary>
    /// This service modify or extend the service across an endpoint.
    /// </summary>
    /// <param name="endpoint">The endpoint that exposes the contract.</param>
    /// <param name="endpointDispatcher">The endpoint dispatcher to be
    /// modified or extended.</param>
    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, 
                                      EndpointDispatcher endpointDispatcher)
    {
      // add inspector which detects cross origin requests
      endpointDispatcher.DispatchRuntime.MessageInspectors.Add(
                                             new MessageInspector(endpoint));
    }

   public void ApplyClientBehavior(ServiceEndpoint endpoint,
                                   ClientRuntime clientRuntime) { }

   public void Validate(OperationDescription operationDescription) { }

   public void ApplyDispatchBehavior(OperationDescription operationDescription,
                                     DispatchOperation dispatchOperation) { }

   public void ApplyClientBehavior(OperationDescription operationDescription,
                                   ClientOperation clientOperation) { }

   public void AddBindingParameters(OperationDescription operationDescription,
                             BindingParameterCollection bindingParameters) { }

  }
}

在此之后，您需要做的就是将此消息检查器添加到服务端点行为中。

ServiceHost host = new ServiceHost(typeof(myService), _baseAddress);
foreach (ServiceEndpoint EP in host.Description.Endpoints)
            EP.Behaviors.Add(new BehaviorAttribute());

谢谢大家的帮助。