.NET Web API CORS 预检请求

我在向其他域上的 Web API 发出 PUT 和 DELETE CORS 请求时遇到一些问题。

我已经通过教程编写了 APIhttp://www.asp.net/web-api/overview/security/enabling-cross-origin-requests-in-web-api#create-webapi-project http://www.asp.net/web-api/overview/security/enabling-cross-origin-requests-in-web-api#create-webapi-project.

GET 和 POST 请求工作正常，但 DELETE 和 PUT 则不行。我收到这条消息：

Failed to load resource: the server responded with a status of 405 (Method Not Allowed)
Failed to load resource: No 'Access-Control-Allow-Origin' header is present on the requested resource.

当我将代码添加到建议的 Web Config 时CORS 支持使用 ASP.NET Web API 进行 PUT 和 DELETE https://stackoverflow.com/questions/12521499/cors-support-for-put-and-delete-with-asp-net-web-api，我只得到第一个错误。

有人可以帮我解决这个问题吗？

您可以添加一个处理程序来处理此类请求。

创建一个从“DelegatingHandler”派生的类：

public class PreflightRequestsHandler : DelegatingHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        if (request.Headers.Contains("Origin") && request.Method.Method.Equals("OPTIONS"))
        {
            var response = new HttpResponseMessage { StatusCode = HttpStatusCode.OK };
            // Define and add values to variables: origins, headers, methods (can be global)               
            response.Headers.Add("Access-Control-Allow-Origin", origins);
            response.Headers.Add("Access-Control-Allow-Headers", headers);
            response.Headers.Add("Access-Control-Allow-Methods", methods);
            var tsc = new TaskCompletionSource<HttpResponseMessage>();
            tsc.SetResult(response);
            return tsc.Task;
        }
        return base.SendAsync(request, cancellationToken);
    }

}

稍后在 WebApiconfig.cs 的 Register 方法中添加以下内容：

public static void Register(HttpConfiguration config)
{
    // Define and add values to variables: origins, headers, methods (can be global) 
    // Enable global CORS
    config.EnableCors(new EnableCorsAttribute(origins, headers, methods));

    // Add handler to deal with preflight requests, this is the important part
    config.MessageHandlers.Add(new PreflightRequestsHandler()); // Defined above
    .
    .
    .
}