C# 如何在HttpClient中使用request.AddParameter（restsharp）

我有这个代码，并且工作过

string userName = "username";
        string password = "password";
        string clientSecret = "clientSecretCode";
        var client = new RestClient("url");
        var request = new RestRequest(Method.POST);
        request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
        request.AddParameter("undefined",
            $"grant_type=password&username={userName}&password={password}&client_id=mmp-web-api&client_secret={clientSecret}&scope=openid%20mmp-webpanel",
            ParameterType.RequestBody);
        IRestResponse response = client.Execute(request);
        var result = JsonConvert.DeserializeObject<TokenOutputDto>(response.Content);

如何将此代码转换为httpclient（在没有RestSharp的情况下运行）

string userName=“userName”；
字符串password=“password”；
字符串clientSecret=“clientSecretCode”；
HttpClient HttpClient=新HttpClient（）；
Uri requestUri=新Uri（“您的完整URL”）；
httpClient.DefaultRequestHeaders
接受
.Add（新的MediaTypeWithQualityHeaderValue（“application/x-www-form-urlencoded”）//接受标题
//参数
var content=newformurlencodedcontent（new[]
{
新的KeyValuePair（“undefined”、$“grant_type=password&username={username}&password={password}&client_id=mmp web api&client_secret={clientSecret}&scope=openid%20mmp webpanel”）
});
var response=httpClient.PostAsync（requestUri.ToString（），content）.Result；
var token=response.Content.ReadAsStringAsync（）.Result；
var result=JsonConvert.DeserializeObject（令牌）；

public class TokenOutputDto
{
    public string access_token { get; set; }
}

string userName = "username";
            string password = "password";
            string clientSecret = "clientSecretCode";

            HttpClient httpClient = new HttpClient();
            Uri requestUri = new Uri("Your Complete URL");
            httpClient.DefaultRequestHeaders
                .Accept
                .Add(new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));//ACCEPT header

            // Parameter
            var content = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("undefined", $"grant_type=password&username={userName}&password={password}&client_id=mmp-web-api&client_secret={clientSecret}&scope=openid%20mmp-webpanel")
            });

            var response = httpClient.PostAsync(requestUri.ToString(), content).Result;
            var token = response.Content.ReadAsStringAsync().Result;
            var result = JsonConvert.DeserializeObject<TokenOutputDto>(token);