求助：将JavaScript API POST请求转换为C#并验证代码正确性

原JavaScript请求代码 #

const echoPostRequest = {
  url: 'https://'+ pm.environment.get('apigw') +'/token',
  method: 'POST',
  header: 'Content-Type:application/json',
  header: 'Authorization: Basic '+ base64EncodedPassword,
 body: {
          mode: 'urlencoded',
          urlencoded: [
            {key: "grant_type", value: "client_credentials", disabled: false},
            {key: "scope", value: "scope_test", disabled: false}
        ]
      }
};

你编写的C#代码 #

//This code is just for generating a base-64 code from a string
string basicToken = ClientID+ ":" +ClientSecret;
var basicBytes = System.Text.Encoding.UTF8.GetBytes(basicToken);
string basic = Convert.ToBase64String(basicBytes);
//this is the rest api call
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", basic);
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, TokenUri);

var postData = new
{
        grant_type= "client_credentials",
        scope= "scope-test"
    
};

var content = new StringContent(JsonConvert.SerializeObject(postData), Encoding.UTF8, "application/x-www-form-urlencoded");
request.Content = content;
var response = await client.SendAsync(request);

代码问题分析与修正 #

你的C#代码存在两个核心问题：

• 请求体格式错误：将对象序列化为JSON字符串后，用application/x-www-form-urlencoded作为Content-Type，会导致服务端收到JSON格式字符串，而非标准URL编码键值对（如grant_type=client_credentials&scope=scope-test）。
• 原JS代码的Header冲突：原JS中重复设置header属性，最后仅Authorization头生效，Content-Type:application/json被覆盖，实际请求的Content-Type应为application/x-www-form-urlencoded（因请求体是urlencoded格式）。

修正后的C#代码 #

// 生成Basic认证Token
string basicToken = $"{ClientID}:{ClientSecret}";
var basicBytes = System.Text.Encoding.UTF8.GetBytes(basicToken);
string basic = Convert.ToBase64String(basicBytes);

// 初始化HttpClient（建议复用实例，避免频繁创建导致Socket资源泄漏）
using HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", basic);

// 构造URL编码的请求体键值对
var postData = new Dictionary<string, string>
{
    { "grant_type", "client_credentials" },
    { "scope", "scope_test" } // 注意与原JS的scope值保持一致，原JS为scope_test
};

// 使用FormUrlEncodedContent自动处理URL编码及Content-Type头
var content = new FormUrlEncodedContent(postData);
var response = await client.PostAsync(TokenUri, content);

// 可选：读取响应内容
string responseContent = await response.Content.ReadAsStringAsync();

关键说明 #

• 用FormUrlEncodedContent替代StringContent：它会自动将键值对编码为key1=value1&key2=value2格式，并自动设置Content-Type: application/x-www-form-urlencoded请求头，无需手动处理编码逻辑。
• 原JS的Content-Type:application/json无效：因JS对象重复赋值header，该头会被覆盖，实际请求不会携带此头，C#代码无需设置。
• 注意scope值匹配：原JS中为scope_test，你写的代码里是scope-test，若API要求严格匹配，需修正为与原JS一致的值。

内容的提问来源于stack exchange，提问作者Hamid Elouardaoui