//方法1. Post 异步请求，普通的异步请求，传输普通的字符串等，对于有html代码的字段值的传输支持不好，如果需要传输html，二进制等数据的传输，请使用下面第二个方法，即使用UploadDataAsync

using (var client = new WebClient())
{
var paramJson = ObjectToJson(emailModel);
client.Headers[HttpRequestHeader.ContentType] = "application/json";
cli.UploadStringAsync(new Uri(url), paramJson);
}

//方法2. Post 异步请求，emailModel实体可包含byte[]的字段值

using (var client = new WebClient())
{
var paramJson = ObjectToJson(emailModel);
client.Headers[HttpRequestHeader.ContentType] = "application/json";
var bytes = Encoding.UTF8.GetBytes(paramJson);
client.UploadDataAsync(new Uri(url), "POST", bytes);
}

public static string ObjectToJson(object obj)
{
JavaScriptSerializer jsonSerialize = new JavaScriptSerializer();
return jsonSerialize.Serialize(obj);
}

方法3. 使用RestSharp第三方库dll发起Http请求，emailModel实体可包含byte[]的字段值，Rest会自动处理传输数据，进行序列化

var model = new { Name = "NotifyAdminPlaceOrder", Subject = "<%CompanyName%> Cash Exercise行权管理", Body = emailModel.Parameters["@Content"] };
string url2 = "https://localhost:44300/system/GenerateMailTemplate";
var request = new RestRequest();
request.RequestFormat = DataFormat.Json;
request.AddBody(model);
var restClient = new RestClient(url2);
restClient.PostAsync(request, null);

C#发起Http请求,调用接口