我将一些代码从网站中分离出来,在复制了相关特定页面后面的代码后,我在PostAsJsonAsync()
代码行中收到错误:
HttpResponseMessage response = await client.PostAsJsonAsync("api/...", user);
在此using语句中(也添加了标题)
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Mail;
using System.Threading.Tasks;
//...
using (var client = new HttpClient())
{
client.BaseAddress = new Uri("WebServiceAddress");
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response = await client.PostAsJsonAsync("api/...", user);
if (response.IsSuccessStatusCode)
{
const string result = "Thank you for your submission.";
return result;
}
//...
}
我得到的错误是
Error 4 'System.Net.Http.HttpClient'
does not contain a definition for 'PostAsJsonAsync' and no extension
method 'PostAsJsonAsync' accepting a first argument of type 'System.Net.Http.HttpClient'
could be found (are you missing a using directive or an assembly reference?)
即使它在前一个项目中有效,也完全从该项目中复制过来。我忘了添加一些东西吗?
我很感激有关此事的任何帮助。
答案 0 :(得分:26)
您必须添加以下依赖项
System.Net.Http.Formatting.dll
它应该在扩展中 - >组装
或
您可以添加Microsoft.AspNet.WebApi.Client
nuget包
答案 1 :(得分:2)
我编写了自己的扩展方法,因为我认为该方法仅适用于较旧的.NET API,并使用了Newtonsoft JSON序列化程序:
// Extension method to post a JSON
public static async Task<HttpResponseMessage> PostAsJsonAsync(this HttpClient client, string addr, object obj)
{
var response = await client.PostAsync(addr, new StringContent(
Newtonsoft.Json.JsonConvert.SerializeObject(obj),
Encoding.UTF8, "application/json"));
return response;
}
答案 2 :(得分:0)
即使安装了相应的Nuget包,我也遇到了同样的错误。帮助我的只是using
声明:
using System.Net.Http;