C#API解决自定义请求头下的跨域问题

解决方法一：

1public class CrosHandler : DelegatingHandler
2    {
3        private const string Origin = "Origin";
4        private const string AccessControlRequestMethod = "Access-Control-Request-Method";
5        private const string AccessControlRequestHeaders = "Access-Control-Request-Headers";
6        private const string AccessControlAllowOrign = "Access-Control-Allow-Origin";
7        private const string AccessControlAllowMethods = "Access-Control-Allow-Methods";
8        private const string AccessControlAllowHeaders = "Access-Control-Allow-Headers";
9        private const string AccessControlAllowCredentials = "Access-Control-Allow-Credentials";
10
11        /// <summary>
12        /// 异步发送 HTTP 请求到要发送到服务器的内部处理程序
13        /// </summary>
14        /// <param name="request"></param>
15        /// <param name="cancellationToken"></param>
16        /// <returns></returns>
17        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
18        {
19            bool isCrosRequest = request.Headers.Contains(Origin);
20            //是否预请求
21            bool isPrefilightRequest = request.Method == HttpMethod.Options;
22            if (isCrosRequest)
23            {
24                Task<HttpResponseMessage> taskResult = null;
25                if (isPrefilightRequest)
26                {
27                    taskResult = Task.Factory.StartNew<HttpResponseMessage>(() =>
28                    {
29                        HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.Accepted);
30                        response.Headers.Add(AccessControlAllowOrign, request.Headers.GetValues(Origin).FirstOrDefault());
31
32                        string method = request.Headers.GetValues(AccessControlRequestMethod).FirstOrDefault();
33                        if (!string.IsNullOrEmpty(method))
34                        {
35                            response.Headers.Add(AccessControlAllowMethods, method);
36                        }
37
38                        string headers = string.Join(", ", request.Headers.GetValues(AccessControlRequestHeaders));
39                        if (!string.IsNullOrEmpty(headers))
40                        {
41                            response.Headers.Add(AccessControlAllowHeaders, headers);
42                        }
43
44                        response.Headers.Add(AccessControlAllowCredentials, "true");
45                        return response;
46                    }, cancellationToken);
47                }
48                else
49                {
50                    taskResult = base.SendAsync(request, cancellationToken).ContinueWith<HttpResponseMessage>(t =>
51                    {
52                        var response = t.Result;
53                        response.Headers.Add(AccessControlAllowOrign, request.Headers.GetValues(Origin).FirstOrDefault());
54                        response.Headers.Add(AccessControlAllowCredentials, "true");
55                        return response;
56                    }, cancellationToken);
57                }
58                return taskResult;
59            }
60            return base.SendAsync(request, cancellationToken);
61        }
62    }

调用：

调用方式：在Global.asax文件的Application_Start方法添加GlobalConfiguration.Configuration.MessageHandlers.Add(new CrosHandler());或者在WebApiConfig.cs下面添加：config.MessageHandlers.Add(new CrosHandler());

解决方法二：

在Web.config下的<system.webServer>节点之间添加一下代码：

1<httpProtocol>
2          <customHeaders>
3            <add name="Access-Control-Allow-Origin" value="*" />
4            <add name="Access-Control-Allow-Headers" value="Access-Control-Allow-Origin, AppKey, Authorization" />
5            <add name="Access-Control-Allow-Methods" value="GET, POST, OPTIONS" />
6            <add name="Access-Control-Request-Methods" value="GET, POST, OPTIONS" />
7          </customHeaders>
8       </httpProtocol>