在WCF服务上从AJAX进行REST请求期间，在CORS中启用OPTIONS方法 [英] Enabling OPTIONS method in CORS during REST request from AJAX on WCF Service

问题描述

我已经摸索了7个小时，试图弄清楚这一点.我在网上搜索了所有内容，但没有运气.我有一个Angular App，它正在向WCF命令行托管服务应用程序发出请求.通过使用以下两个类，我设法通过了CORS:

I have scratched my head for 7 hours trying to figure this out. I have searched all over the web but no luck. I have an Angular App that is making requests to a WCF command-line hosted service application. I managed to get by CORS by using these two classes:

public class CustomHeaderMessageInspector : IDispatchMessageInspector
{
    Dictionary<string, string> requiredHeaders;

    public CustomHeaderMessageInspector(Dictionary<string, string> headers)
    {
        requiredHeaders = headers ?? new Dictionary<string, string>();
    }

    public object AfterReceiveRequest(ref Message request, 
    System.ServiceModel.IClientChannel channel, 
    System.ServiceModel.InstanceContext instanceContext)
    {
        return null;
    }

    public void BeforeSendReply(ref Message reply, object correlationState)
    {
        var httpHeader = reply.Properties["httpResponse"] as HttpResponseMessageProperty;
        foreach (var item in requiredHeaders)
        {
            httpHeader.Headers.Add(item.Key, item.Value);
        }
    }
}

并且:

public class EnableCorsBehavior : BehaviorExtensionElement, IEndpointBehavior
{
    public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
    { }

    public void ApplyClientBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.ClientRuntime clientRuntime)
    { }

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.EndpointDispatcher endpointDispatcher)
    {
        var requiredHeaders = new Dictionary<string, string>();

        requiredHeaders.Add("Access-Control-Allow-Origin", "*");
        requiredHeaders.Add("Access-Control-Request-Method", "POST,GET,PUT,DELETE,OPTIONS");
        requiredHeaders.Add("Access-Control-Allow-Headers", "X-Requested-With,Content-Type");

        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new CustomHeaderMessageInspector(requiredHeaders));
    }

    public void Validate(ServiceEndpoint endpoint) { }

    public override Type BehaviorType
    {
        get { return typeof(EnableCorsBehavior); }
    }

    protected override object CreateBehavior()
    {
        return new EnableCorsBehavior();
    }
}

将此自定义扩展名添加到app.config文件中解决了我的CORS问题.我当前的问题是，每当我发出POST请求时，都会收到错误消息:

Adding this custom extension to the app.config file solved my CORS problem. My current problem is whenever I make a POST request, I get the error:

Request Method:OPTIONS
Status Code:405 Method Not Allowed

我对C#还是很陌生，我似乎找不到在哪里放置可以让我超越此范围的代码.我有一个想法，应该将其放置在BeforeSendReply()方法中的某个位置.请帮我！我真的会很感激！

I am quite new to C# and I can't seem to find where to place the code that will allow me to get past this. I have an idea that it should be placed somewhere in the BeforeSendReply() method. Please help me! I will really really appreciate it!

致谢！

推荐答案

我想出了解决方案，希望这对遇到同一问题的所有人有所帮助.在我在问题中发布的 CustomHeaderMessageInspector 类中，我在 AfterReceiveRequest 方法中编辑了以下代码，如下所示:

I figured out the solution to this and i hope this helps everyone who comes across this same issue. In the CustomHeaderMessageInspector class that I posted in the question, I edited the following code in the AfterReceiveRequest method as follows:

// return null;
var httpRequest = (HttpRequestMessageProperty)request
    .Properties[HttpRequestMessageProperty.Name];
return new
{
    origin = httpRequest.Headers["Origin"],
    handlePreflight = httpRequest.Method.Equals("OPTIONS",
    StringComparison.InvariantCultureIgnoreCase)
};

我希望代码所做的是使用OPTIONS方法监视任何请求，并以预检状态对其进行标记".然后，我修改了 BeforeSendReply 中的代码，如下所示:

What I hoped that code did is monitor any request with the OPTIONS method and "tag" it with a preflight state. Then I modified the code in the BeforeSendReply to look as follows:

var state = (dynamic)correlationState;
if (state.handlePreflight)
{
    reply = Message.CreateMessage(MessageVersion.None, "PreflightReturn");

    var httpResponse = new HttpResponseMessageProperty();
    reply.Properties.Add(HttpResponseMessageProperty.Name, httpResponse);

    httpResponse.SuppressEntityBody = true;
    httpResponse.StatusCode = HttpStatusCode.OK;
}

var httpHeader = reply.Properties["httpResponse"] as HttpResponseMessageProperty;
foreach (var item in requiredHeaders)
{
    httpHeader.Headers.Add(item.Key, item.Value);
}

(我希望)这样做是获得带有OPTIONS标签的任何请求，并通过返回200状态代码来处理该请求.这终于使它起作用了，我希望它能对某人有所帮助！

What that does (i hope) is get any request tagged with OPTIONS and handle it by returning a 200 status code. This got it finally working and I hope it helps someone!

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