c# - DeleteAsync和PostAsync不起作用

Question

我写了这个可以正常工作的PutAsync，可以让我更新数据库中的项目:

private async void Edit()
{
    using (HttpClient client = new HttpClient())
    {
        Item i = new Item();
        i.ID = SelectedItem.ID;
        i.Name = SelectedItem.Name;
        i.Cost = SelectedItem.Cost;

        string json = JsonConvert.SerializeObject(i);

        HttpResponseMessage response = await client.PutAsync("http://localhost:5065/api/item", new StringContent(json, Encoding.UTF8, "application/json"));
        if (response.IsSuccessStatusCode)
        {
            string jsonresponse = await response.Content.ReadAsStringAsync();
            int result = JsonConvert.DeserializeObject<int>(jsonresponse);
            if (result == 2)
            {
                GetItems();
            }
        }
    }
}

现在，我想删除项目并添加新项目，但是此代码似乎不起作用:

public ICommand DeleteCommand
{
    get { return new RelayCommand(Delete); }
}

private async void Delete()
{
    using (HttpClient client = new HttpClient())
    {
        Item i = new Item();
        i.ID = SelectedItem.ID;
        i.Name = SelectedItem.Name;
        i.Cost = SelectedItem.Cost;

        HttpResponseMessage response = await client.DeleteAsync("http://localhost:5065/api/item/" + i.ID );
        if (response.IsSuccessStatusCode)
        {
            string jsonresponse = await response.Content.ReadAsStringAsync();
            int result = JsonConvert.DeserializeObject<int>(jsonresponse);
            if (result == 2)
            {
                GetItems();
            }
        }
    }
}

我的PostAsync也是如此:

private async void New()
{
    using (HttpClient client = new HttpClient())
    {     
        Item i = new Item();
        i.Name = SelectedItem.Name;
        i.Cost = SelectedItem.Cost;

        string json = JsonConvert.SerializeObject(i);

        HttpResponseMessage response = await client.PostAsync("http://localhost:5065/api/item", new StringContent(json, Encoding.UTF8, "application/json"));
        if (response.IsSuccessStatusCode)
        {
            string jsonresponse = await response.Content.ReadAsStringAsync();
            int result = JsonConvert.DeserializeObject<int>(jsonresponse);
            if (result == 2)
            {
                GetItems();
            }
        }
    }
}

我得到以下回应:

{StatusCode: 204, ReasonPhrase: 'No Content', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:{  Pragma: no-cache  X-SourceFiles: =?UTF-8?B?RDpcU0NIT09MXE5NQ1QgTGFhdHN0ZVxCdXNpbmVzcyBhcHBsaWNhdGlvbnNcUFJPSkVDVFxQcm9qZWN0XFByb2plY3QuYXBpXGFwaVxwcm9kdWN0XDU=?=  Cache-Control: no-cache  Date: Mon, 19 Jan 2015 13:48:32 GMT  Server: Microsoft-IIS/8.0  X-AspNet-Version: 4.0.30319  X-Powered-By: ASP.NET  Expires: -1}}

我做错了什么，我该如何进行发布和删除工作？

编辑:
这是Delete void的一些服务器端代码，非常基本:

public static int DeleteItem(int id)
        {
            int rowsaffected = 0;
            DbTransaction trans = null;

            try
            {
                trans = Database.BeginTransaction("ConnectionString");

                string sql = "DELETE FROM Item WHERE ID=@ID";
                DbParameter par1 = Database.AddParameter("ConnectionString", "@ID", id);
                rowsaffected += Database.ModifyData(trans, sql, par1);

                trans.Commit();
            }
            catch (Exception ex)
            {
                if (trans != null)
                    trans.Rollback();
            }
            finally
            {
                if (trans != null)
                    Database.ReleaseConnection(trans.Connection);
            }

            return rowsaffected;
        }

我在这里称呼它:

   // DELETE: api/Item/5
        public void Delete(int id)
        {
            ItemDataAccess.DeleteItem(id);
        }

编辑:
也许一些额外的信息，在下一行

int result = JsonConvert.DeserializeObject<int>(jsonresponse);

在两种情况下，我都会收到此错误:

A first chance exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in Newtonsoft.Json.dll

Additional information: No JSON content found and type 'System.Int32' is not nullable. Path '', line 0, position 0.

Answer 1

您的调用成功，204是一个成功代码，告诉客户不要在体内获取任何数据。您没有从消息中返回任何内容，因此服务器会在204中自动填充Controller方法中的void类型。