httpClient 顯示錯誤 c# winform

Question

我有以下代碼，但它的顯示錯誤我使用的是框架 4.5。 請幫忙 。

var baseAddress = new Uri("http://private-5e199-karhoofleetintegration.apiary-mock.com/");

using (var httpClient = new HttpClient { BaseAddress = baseAddress })
{
    httpClient.DefaultRequestHeaders.TryAddWithoutValidation("accept-charset", "utf-8");

    httpClient.DefaultRequestHeaders.TryAddWithoutValidation("authorization", "Basic *sample_token*");

    using (var content = new StringContent("{  \"vehicles\": [    {      \"vehicle_type\": \""+ vehicale_type +"\",      \"vehicle_id\": \"" +vehicle_id+"\",  "\"heading\": 90      }    }  ]}", System.Text.Encoding.Default, "application/json"))
    {
        using (var response = await httpClient.PostAsync("{supplier_id}/availability?version=2", content))
        {
            string responseData = await response.Content.ReadAsStringAsync();
        }
    }
}

Answer 1

要使用 async/await 內容，您需要使用async關鍵字標記您的方法。

如果您的方法是事件處理程序，則使用async void ，如果不是，則使用async Task或async Task<ReturnType> 。 （確保用您的方法返回的實際類型替換“ReturnType”）

例子：

public async Task GetDataFromTheWeb()
//     ^^^^^ add this keyword
{
    var baseAddress = new Uri("http://private-5e199-karhoofleetintegration.apiary-mock.com/");

    using (var httpClient = new HttpClient { BaseAddress = baseAddress })
    {
        httpClient.DefaultRequestHeaders.TryAddWithoutValidation("accept-charset", "utf-8");

        httpClient.DefaultRequestHeaders.TryAddWithoutValidation("authorization", "Basic *sample_token*");

        using (var content = new StringContent("{  \"vehicles\": [    {      \"vehicle_type\": \""+ vehicale_type +"\",      \"vehicle_id\": \"" +vehicle_id+"\",  "\"heading\": 90      }    }  ]}", System.Text.Encoding.Default, "application/json"))
        {
            using (var response = await httpClient.PostAsync("{supplier_id}/availability?version=2", content))
            {
                string responseData = await response.Content.ReadAsStringAsync();
            }
        }
    }
}