使WebClient().DownloadString异步

Question

如何使这段代码不阻塞异步，使其不阻塞UI？我需要再用一个图书馆吗？

public static double GetRsi(string symbol1, string interval1, string period1)
            {
                //API KEY FROM alphavantage.co
                string API_KEY = "xxxxxxx";
                
                StringBuilder urlBuilder = new StringBuilder();
                urlBuilder.Append($"https://www.alphavantage.co/");
                urlBuilder.Append($"query?function=RSI&symbol={symbol1}&interval={interval1}&time_period={period1}&series_type=open&apikey={API_KEY}");
                string jsonData = new WebClient().DownloadString(urlBuilder.ToString());
    
    
                var machine = JsonConvert.DeserializeObject<AlphavantageData>(jsonData);
                var _RSI = machine.TechnicalAnalysisRsi.Last().Value.Rsi;
                return _RSI; 
            }

Answer 1

WebClient有一个可以使用的DownloadStringTaskAsync：

public static async Task<double> GetRsi(string symbol1, string interval1, string period1)
{
    //API KEY FROM alphavantage.co
    string API_KEY = "xxxxxxx";
    
    StringBuilder urlBuilder = new StringBuilder();
    urlBuilder.Append($"https://www.alphavantage.co/");
    urlBuilder.Append($"query?function=RSI&symbol={symbol1}&interval={interval1}&time_period={period1}&series_type=open&apikey={API_KEY}");
    
    using(var webClient = new WebClient())
    {
        string jsonData = await webClient.DownloadStringTaskAsync(urlBuilder.ToString());

        var machine = JsonConvert.DeserializeObject<AlphavantageData>(jsonData);
        var _RSI = machine.TechnicalAnalysisRsi.Last().Value.Rsi;
        return _RSI; 
    }
}

Answer 2

您可以像前面建议的那样使用DownloadStringTaskAsync。我还想提到，在现代C#/.NET代码中不推荐使用WebClient。试一试System.Net.Http.HttpClient。它更轻，是async从开始。

请看一下msdn。

示例：

// You need 1 client per application
static readonly HttpClient client = new HttpClient();

...
var url = $"https://www.alphavantage.co/query?function=RSI&symbol={symbol1}&interval={interval1}&time_period={period1}&series_type=open&apikey={API_KEY}";
var response = await client.GetStringAsync(url);