目前，为了向一个API接口发送带参数的GET请求，我正在编写以下代码：
api/master/city/filter?cityid=1&citycode='ny'
但我发现URL长度有2083个字符的限制。
为了避免这种情况，我希望用json格式发送参数到GET请求的内容体中。
然而，我发现HttpClient的所有Get方法都不允许发送内容体。对于POST方法，我可以看到HttpClient中有一个名为PostAsync的方法可以发送内容体。
是否存在一种方式，可以在不使用URL的情况下发送GET请求的参数，以避免URL长度的限制？
If you are using .NET Core, the standard HttpClient can do this out-of-the-box. For example, to send a GET request with a JSON body:
HttpClient client = ...
...
var request = new HttpRequestMessage
{
Method = HttpMethod.Get,
RequestUri = new Uri("some url"),
Content = new StringContent("some json", Encoding.UTF8, MediaTypeNames.Application.Json /* or "application/json" in older versions */),
};
var response = await client.SendAsync(request).ConfigureAwait(false);
response.EnsureSuccessStatusCode();
var responseBody = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
.NET Framework doesn't support this out-of-the-box (you will receive a ProtocolViolationException if you try the above code). Thankfully Microsoft has provided the System.Net.Http.WinHttpHandler package that does support the functionality - simply install and use it instead of the default HttpClientHandler when constructing your HttpClient instances:
var handler = new WinHttpHandler();
var client = new HttpClient(handler);
<rest of code as above>
Reference: https://github.com/dotnet/runtime/issues/25485#issuecomment-467261945
注意事项：
ContentType.Json 时一直出现错误，所以我不得不使用 "application/json"。 - computercarguy我无法使用.NET Core，也不想安装 System.Net.Http.WinHttpHandler，因为它有很多依赖项。我通过使用反射解决了这个问题，欺骗 WebRequest 发送正文内容是合法的 GET 请求（这是根据最新的 RFC）。我所做的是将 HTTP 动词“GET”的 ContentBodyNotAllowed 设置为 false。
var request = WebRequest.Create(requestUri);
request.ContentType = "application/json";
request.Method = "GET";
var type = request.GetType();
var currentMethod = type.GetProperty("CurrentMethod", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(request);
var methodType = currentMethod.GetType();
methodType.GetField("ContentBodyNotAllowed", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(currentMethod, false);
using (var streamWriter = new StreamWriter(request.GetRequestStream()))
{
streamWriter.Write("<Json string here>");
}
var response = (HttpWebResponse)request.GetResponse();
请注意，属性 ContentBodyNotAllowed 属于静态字段，因此当其值更改时，其影响将在整个程序中保持不变。对于我的目的来说，这不是问题。
ContentBodyNotAllowed）。 - Ian Kemp var request = WebRequest.Create(requestUri);
System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
request.ContentType = "application/json";
request.Method = "GET";
request.Headers.Add("Authorization", "Bearer " + Token);
var type = request.GetType();
var currentMethod = type.GetProperty("CurrentMethod", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(request);
var methodType = currentMethod.GetType();
methodType.GetField("ContentBodyNotAllowed", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(currentMethod, false);
using (var streamWriter = new StreamWriter(request.GetRequestStream()))
{
streamWriter.Write(JsonConvert.SerializeObject(Entity));
}
var response = request.GetResponse();
var responseStream = response.GetResponseStream();
if (responseStream != null)
{
var myStreamReader = new StreamReader(responseStream, Encoding.Default);
var resultEntity= myStreamReader.ReadToEnd();
myStreamReader.ReadToEnd());
}
responseStream.Close();
response.Close();
花了很多时间后，我无法使HttpClient和WebRequest在我的.Net Core项目中工作，明显地，服务器没有获取到我的数据，并返回一个错误，说我的请求中缺少某些特定的数据。最终，只有RestSharp在我的情况下起作用（以下代码中的变量myData是一个Dictionary<string，string>实例）：
var client = new RestClient("some url");
var request = new RestRequest(Method.GET);
foreach (var d in myData)
request.AddParameter(d.Key, d.Value);
var result = (await client.ExecuteAsync(request)).Content;
类似于上面的答案，但代码更简洁
var request = new HttpRequestMessage
{
Method = HttpMethod.Get,
RequestUri = targetUri,
Content = new StringContent(payload.Payload),
};
var response = await client.SendAsync(request).ConfigureAwait(false);
var responseInfo = await response.Content.ReadAsStringAsync();