c# - 使用 MultipartFormDataContent 生成错误的 Content-Type header

Question

我有以下代码:

private static string boundary = "----CustomBoundary" + DateTime.Now.Ticks.ToString("x");

private static async Task<string> PostTest()
{
    string servResp = "";

    using (var content = new MultipartFormDataContent(boundary))
    {
        content.Add(new StringContent("105212"), "case-id");
        content.Add(new StringContent("1/14/2014"), "dateFrom");
        content.Add(new StringContent("1/15/2014"), "dateTo");

        HttpClientHandler handler = new HttpClientHandler();
        cookieContainer = new CookieContainer();
        handler.CookieContainer = cookieContainer;

        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, "http://somewebsite.com/form");
        request.Headers.ExpectContinue = false;
        request.Content = content;

        httpClient = new HttpClient(handler);

        HttpResponseMessage response = await httpClient.SendAsync(request);
        response.EnsureSuccessStatusCode();

        servResp = await response.Content.ReadAsStringAsync();
    }

    return servResp;
}

当我运行它时，我在 Fiddler 中看到了 Content-Type header :

Content-Type: multipart/form-data; boundary="----CustomBoundary8d0f01e6b3b5daf"

因为边界值在引号中，所以服务器会忽略请求正文。如果我删除引号并在 Fiddler Composer 中运行请求，请求将得到正确处理。

我尝试添加内容标题:

//request.Content.Headers.Add("Content-Type", "multipart/form-data; boundary=" + boundary);
//request.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("multipart/form-data; boundary=" + boundary);

... 但它没有用，错误消息是:“无法添加值，因为 header ‘Content-Type’不支持多个值。”和“值‘multipart/form-data，boundary=----CustomBoundary8d0f024297b32d5’的格式无效。”，相应地。

如何将正确的 Content-Type header 添加到请求中，以便边界值不包含在引号中？

Content-Type: multipart/form-data; boundary=----CustomBoundary8d0f01e6b3b5daf

Answer 1

通过从 MultipartFormDataContent 中删除标题并在不验证的情况下重新添加它来解决此问题:

content.Headers.Remove("Content-Type");
content.Headers.TryAddWithoutValidation("Content-Type", "multipart/form-data; boundary=" + boundary);