如何在 Web API 消息处理程序中提取自定义标头值?

问题描述

我目前在我的 Web API 服务中有一个消息处理程序，它覆盖SendAsync"，如下所示:

I currently have a message handler in my Web API service that overrides 'SendAsync' as follows:

protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
  //implementation
}

在此代码中，我需要检查名为 MyCustomID 的自定义添加的请求标头值.问题是当我执行以下操作时:

Within this code I need to inspect a custom added request header value named MyCustomID. The problem is when I do the following:

if (request.Headers.Contains("MyCustomID"))  //OK
    var id = request.Headers["MyCustomID"];  //build error - not OK

...我收到以下错误消息:

...I get the following error message:

不能将带有 [] 的索引应用于类型表达式'System.Net.Http.Headers.HttpRequestHeaders'

如何通过 HttpRequestMessage (MSDN 文档) 实例传递到这个重写的方法?

How can I access a single custom request header via the HttpRequestMessage (MSDN Documentation) instance passed into this overridden method?

推荐答案

试试这个:

IEnumerable<string> headerValues = request.Headers.GetValues("MyCustomID");
var id = headerValues.FirstOrDefault();

如果您不能总是保证可以访问标头，则可以使用标头上的 TryGetValues 方法.

There's also a TryGetValues method on Headers you can use if you're not always guaranteed to have access to the header.

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