public class CrosHandler : DelegatingHandler
{
private const string Origin = "Origin";
private const string AccessControlRequestMethod = "Access-Control-Request-Method";
private const string AccessControlRequestHeaders = "Access-Control-Request-Headers";
private const string AccessControlAllowOrign = "Access-Control-Allow-Origin";
private const string AccessControlAllowMethods = "Access-Control-Allow-Methods";
private const string AccessControlAllowHeaders = "Access-Control-Allow-Headers";
private const string AccessControlAllowCredentials = "Access-Control-Allow-Credentials";
/// <summary>
/// 异步发送 HTTP 请求到要发送到服务器的内部处理程序
/// </summary>
/// <param name="request"></param>
/// <param name="cancellationToken"></param>
/// <returns></returns>
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
bool isCrosRequest = request.Headers.Contains(Origin);
//是否预请求
bool isPrefilightRequest = request.Method == HttpMethod.Options;
if (isCrosRequest)
{
Task<HttpResponseMessage> taskResult = null;
if (isPrefilightRequest)
{
taskResult = Task.Factory.StartNew<HttpResponseMessage>(() =>
{
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.Accepted);
response.Headers.Add(AccessControlAllowOrign, request.Headers.GetValues(Origin).FirstOrDefault());
string method = request.Headers.GetValues(AccessControlRequestMethod).FirstOrDefault();
if (!string.IsNullOrEmpty(method))
{
response.Headers.Add(AccessControlAllowMethods, method);
}
string headers = string.Join(", ", request.Headers.GetValues(AccessControlRequestHeaders));
if (!string.IsNullOrEmpty(headers))
{
response.Headers.Add(AccessControlAllowHeaders, headers);
}
response.Headers.Add(AccessControlAllowCredentials, "true");
return response;
}, cancellationToken);
}
else
{
taskResult = base.SendAsync(request, cancellationToken).ContinueWith<HttpResponseMessage>(t =>
{
var response = t.Result;
response.Headers.Add(AccessControlAllowOrign, request.Headers.GetValues(Origin).FirstOrDefault());
response.Headers.Add(AccessControlAllowCredentials, "true");
return response;
}, cancellationToken);
}
return taskResult;
}
return base.SendAsync(request, cancellationToken);
}
}
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());
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="*" />
<add name="Access-Control-Allow-Headers" value="Access-Control-Allow-Origin, AppKey, Authorization" />
<add name="Access-Control-Allow-Methods" value="GET, POST, OPTIONS" />
<add name="Access-Control-Request-Methods" value="GET, POST, OPTIONS" />
</customHeaders>
</httpProtocol>