C＃WP8：如何连续调用异步任务方法并每次都获得新的响应？

Question

This method:

 public async Task<string> GetjsonStream(string url)
    {
        HttpClient client = new HttpClient();
        HttpResponseMessage response = await client.GetAsync(url);
        string content = await response.Content.ReadAsStringAsync();
        return content;
    }

Is called by this method:

private async void button_Click(object sender, RoutedEventArgs e)
    {
        String URL = URL_core + API_call;
        try
        {
            string response = await GetjsonStream(URL);
            JSONReturn answere = JsonConvert.DeserializeObject<JSONReturn>(response);
            output_box.Text = answere.value;

        }
        catch (Exception ex)
        {
            output_box.Text = URL;
        }
    }

I am trying to have an API call happen every time a button is pressed on a page. I want to be able to keep pressing the button without re-loading the page and get a new result. However, right now I get the same response from the "GetjsonStream" method every time I press the button.

I am pretty sure I am mis-handling the async method. It seems like I need to either force a wait for it or initiate a fresh instance of the task. I am still new to C# and am learning as I go along, so I'm hoping there is just something obvious that I am missing.

EDIT: Some clarification:

The URL calls a random generator. So it should be a different result every time. When stepping through the "GetjsonStream" method, "content" will be the same every time.

Also, I found that if I wait for a minute or two, and press the button again, I do get a new result. I'm wondering if there is some timeout setting in place.

Answer 1

I am pretty sure I am mis-handling the async method.

No, but you are mishandling HTTP. :)

HTTP gets can be cached. Since the API should always return a different result, the server should be modified to send headers disabling caching.