Web API发送带有对象的POST请求

Question

我是Web api的新手，我似乎无法通过POST从.net项目发送对象。

以下是发送对象的代码：

public async Task<bool> CreateUser (User user)
        {
            Uri uri = new Uri(apiUrl + "api/users");
    var jsonUser = JsonConvert.SerializeObject(user);
            HttpContent content = new StringContent(jsonUser, Encoding.UTF8, "application/json");

            var postUser = await client.PostAsync(uri, content);
            string result = await postUser.Content.ReadAsStringAsync();
            if (postUser.IsSuccessStatusCode)
            {
                return true;
            }

            return false;
        }

这是Web API代码：

[HttpPost]
    public IHttpActionResult Post([FromBody]string jsonUser)
    {
        UserDTO user = JsonConvert.DeserializeObject<UserDTO>(jsonUser);
        bool tryCreate = _userRepository.CreateUser(user);

        if (tryCreate == false)
        {
            return NotFound();
        }
        return Ok();
    }

如果我尝试将POST请求发送到Web api URL，它将成功将json字符串发送到该动作，但是如果我尝试从Web项目发送POST数据，则Content.ReadAsStringAsync()返回：

"{"Message":"An error has occurred.","ExceptionMessage":"Value cannot be null.\r\nParameter name: value","ExceptionType":"System.ArgumentNullException","StackTrace":" at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)\r\n at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)\r\n at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)\r\n at Travue.WebAPI.Controllers.UsersController.Post(String jsonUser) in C:\\Users\\Dev01\\Documents\\projects\\travue\\Travue.WebAPI\\Controllers\\UsersController.cs:line 46\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass6_2.<GetExecutor>b__2(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__15.MoveNext()"}"