在标头C#中设置If-Match

Question

我有Odata服务，为了执行PUT，我们需要在Post man I giving中设置标题，如果匹配：，如下所示

如何在Odata服务调用中设置此If Match以执行PUT操作。我试过下面的

 private async Task<HttpResponseMessage> PutJsonAsync(string messageBody,string B_Code)
 {
 string userName = ConfigurationManager.AppSettings["Username"];
 string password = ConfigurationManager.AppSettings["Password"];
 string BaseURL = ConfigurationManager.AppSettings["BaseURL"];

  try
 {
   using (var httpClient = new HttpClient())
  {
   var request = new StringContent(messageBody, Encoding.UTF8, "application/json");
   string apiUrl = "SAM('" + B_Code + "')";
   request.Headers.ContentType = new MediaTypeHeaderValue("application/json");
   request.Headers.TryAddWithoutValidation("If-Match", "*");
   var url = string.Format("{0}{1}", BaseURL, apiUrl);
   var creds = userName + ":" + password;
   var credentials = Encoding.ASCII.GetBytes(creds);
   httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(credentials));

   response = await httpClient.PutAsync(new Uri(url), request);
 }
}
catch (Exception ex)
{
 throw ex;
  }
   return response;
  }

但它不工作并抛出错误501：未实现

'响应{StatusCode： 501，原因短语：'未实现'，版本：1.1，内容：系统。网。https。流内容，标题：

OData-Version： 4.0日期：周一，2017 20:42:2810月30日格林尼治标准时间设置Cookie： JSESSIONID=XYZ；路径=/；安全；HttpOnly设置Cookie： XYZ；PATH=/；安全；HTTPONLY服务器：Apache-Coyote/1.1变体：接受编码连接：保持活力内容长度：277内容类型：应用程序/json；odata.metadata=最小}}系统。网。Http。Http响应消息'

Answer 1

您的“请求”对象是您的内容对象，而不是HttpRequestMessage对象。我是怎么意识到的？ContentType在HttpRequestMessage上不可用。

如果Match不是内容级别的标题（我不知道Microsoft为什么会做出这种区分）。您不能将其添加到此处，必须将其添加到请求标头。如果将其添加到content对象，则会忽略它。

像这样的方法应该会奏效：

string apiUrl = "SAM('" + B_Code + "')";
var url = string.Format("{0}{1}", BaseURL, apiUrl);
var creds = userName + ":" + password;
var credentials = Encoding.ASCII.GetBytes(creds);
var request = new HttpRequestMessage(HttpMethod.Put, new Uri(url));
request.Content = new StringContent(messageBody, Encoding.UTF8, "application/json");
request.Headers.TryAddWithoutValidation("If-Match", "*");
request.Headers.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(credentials));

response = await httpClient.SendAsync(request);