C# HttpPost 【ContentType：multipart/form-data】表單提交數據方法

var postContent = new MultipartFormDataContent();
postContent.Headers.Add("ContentType", $"multipart/form-data");

//這是【string : string】的鍵值對
postContent.Add(new StringContent(appConfig.apiName), "api_name");

//這是【string : Json】的鍵值對；param是一個類的對象
postContent.Add(new StringContent(param.ToJsonStr()), "content");

//form表單格式傳參

string result = "";

string url = "http://xxxxx.cn";
try
{
　　HttpClient client = new HttpClient();
　　HttpResponseMessage response = client.PostAsync(url, postData).Result;
　　result = response.Content.ReadAsStringAsync().Result;
}
catch (Exception ex)
{
　　result = ex.Message;
}