如何提取网页API消息处理程序自定义头价值？ [英] How to extract custom header value in Web API message handler?

问题描述

我目前在我的Web API服务的消息处理程序，覆盖'SendAsync'如下：

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
}

在这个code我需要检查命名的自定义添加请求头值 MyCustomID 。问题是，当我做到以下几点：

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:

无法适用与[]索引到类型的前pression
  System.Net.Http.Headers.Htt prequestHeaders

Cannot apply indexing with [] to an expression of type 'System.Net.Http.Headers.HttpRequestHeaders'

我怎样才能访问的单的通过自定义请求头中的Htt prequestMessage （ MSDN文档）实例传入此重写的方法？

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

推荐答案

尝试是这样的：

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

还有上一个头的方法TryGetValues​​你可以使用，如果你并不总是保证有机会获得头。

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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