考虑标题名称,如何将HttpRequestBase转换为HttpRequestMessage？

Question

我的包裹HttpRequestBase作为HttpRequestMessage,这就要求所有的头被复制.但由于HttpRequestMessage特定于哪些头应用于请求对象与Content对象,httpRequest.Headers.Add下面的行有时会抛出InvalidOperationException.

public static HttpRequestMessage AsHttpRequestMessage(this HttpRequestBase request) {
    Requires.NotNull(request, "request");

    var httpRequest = new HttpRequestMessage(new HttpMethod(request.HttpMethod), request.Url);
    foreach (string header in request.Headers) {
        httpRequest.Headers.Add(header, request.Headers.GetValues(header));
    }

    if (request.Form != null) {
        // Avoid a request message that will try to read the request stream twice for already parsed data.
        httpRequest.Content = new FormUrlEncodedContent(request.Form.AsKeyValuePairs());
    } else if (request.InputStream != null) {
        httpRequest.Content = new StreamContent(request.InputStream);
    }

    return httpRequest;
}

显然,我希望我的代码不会抛出异常,而是将每个标头适当地应用于适当的对象.我怎么预测呢？我是否可以使用任何方法来测试标题的适用性,而不是生成和捕获异常的标题？

Answer 1

事实证明这很简单.这段代码的灵感源自ASP.NET自己的开源源代码.

/// <summary>
/// Clones an <see cref="HttpWebRequest" /> in order to send it again.
/// </summary>
/// <param name="message">The message to set headers on.</param>
/// <param name="request">The request with headers to clone.</param>
internal static void CopyHeadersFrom(this HttpRequestMessage message, HttpRequestBase request) {
    Requires.NotNull(request, "request");
    Requires.NotNull(message, "message");

    foreach (string headerName in request.Headers) {
        string[] headerValues = request.Headers.GetValues(headerName);
        if (!message.Headers.TryAddWithoutValidation(headerName, headerValues)) {
            message.Content.Headers.TryAddWithoutValidation(headerName, headerValues);
        }
    }
}