Question

我是新手等待异步，我想了解我在这个真实场景中研究过的主题：

我有一个简单的代码，读取比特币价格，需要1-2秒，我不想使用等待异步锁定UI，如果加载或完成仍然给出状态：

    private void button_Click(object sender, RoutedEventArgs e)
    {
        Task<int> bitcoinPriceTask = GetBitcoinPrice();
        lblStatus.Content = "Loading...";
    }

    protected async Task<int> GetBitcoinPrice()
    {
        IPriceRetrieve bitcoin = new BitcoinPrice();
        string price = bitcoin.GetStringPrice();
        txtResult.Text = price;
        lblStatus.Content = "Done";
        return 1;
    }

根据要求，这里是BitcoinPrice类的实现：

public class BitcoinPrice : IPriceRetrieve
{
    public BitcoinPrice()
    {
        Url = "https://www.google.com/search?q=bitcoin%20price";
    }

    public string Url { get; }


    public string GetStringPrice()
    {
        var html = RetrieveContent();
        html = MetadataUtil.GetFromTags(html, "1 Bitcoin = ", " US dollars");
        return html;
    }

    public float GetPrice()
    {
        throw new NotImplementedException();
    }

    public string RetrieveContent()
    {
        var request = WebRequest.Create(Url);
        var response = request.GetResponse();
        var dataStream = response.GetResponseStream();
        var reader = new StreamReader(dataStream);
        var responseFromServer = reader.ReadToEnd();
        return responseFromServer;
    }
}

Answer 1

您的代码现在有很多问题，首先您需要将事件处理程序设置为async，以便您可以等待返回Task<int>的方法，其次可以设置消息加载之前调用方法并等待它，以便它等待该方法完成它，并在它完成工作返回结果时，然后将消息设置为完成：

private async void button_Click(object sender, RoutedEventArgs e)
{
     lblStatus.Content = "Loading...";
     int bitcoinPriceTask = await GetBitcoinPrice();
     lblStatus.Content = "Done";

}

protected async Task<int> GetBitcoinPrice()
{
     IPriceRetrieve bitcoin = new BitcoinPrice();
     string price = await bitcoin.GetStringPrice();
     txtResult.Text = price;
     return 1;
}

或更好的可以返回Task<string>并在事件处理程序中设置TextBox值：

protected async Task<string> GetBitcoinPrice()
{
    IPriceRetrieve bitcoin = new BitcoinPrice();
    string price = await bitcoin.GetStringPrice();
    return price;
}

并在事件处理程序中：

private async void button_Click(object sender, RoutedEventArgs e)
{
     lblStatus.Content = "Loading...";
     string price = await GetBitcoinPrice();
     txtResult.Text = price;
     lblStatus.Content = "Done";

}

在这个WPF示例中使用Async和Await有什么问题？

1 个答案: