DownloadString未被执行

Question

我是C#.Net编程的新手，面临着一个问题。当我调用getLocation函数时，我总是得到"location“为空。我知道我做事情的方式是错误的。但如果有人能帮助我以正确的方式做这件事，那就太好了。我希望getLocation函数返回位置值。因此，它应该只在返回位置值之前执行wc.downloadString时才返回。

public String getLocation()
{
    RetrieveFormatedAddress(latitude, longitutde);
    location = returnVal;
    return location;
}

static void RetrieveFormatedAddress(string lat, string lng)
{
    string requestUri = string.Format(baseUri, lat, lng);

    using (WebClient wc = new WebClient())
    {
        wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted);
        wc.DownloadString(new Uri(requestUri));
        //wc.DownloadStringAsync(new Uri(requestUri));
    }
}

private static void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    var xmlElm = XElement.Parse(e.Result);

    var status = (from elm in xmlElm.Descendants()
                  where elm.Name == "status"
                  select elm).FirstOrDefault();
    if (status.Value.ToLower() == "ok")
    {
        var res = (from elm in xmlElm.Descendants()
                   where elm.Name == "formatted_address"
                   select elm).FirstOrDefault();
        returnVal = res.Value;
    }
    else
    {
        returnVal = "No Address Found";
    }

}

Answer 1

public String getLocation()
{
    return RetrieveFormatedAddress(latitude, longitutde);
}

static string RetrieveFormatedAddress(string lat, string lng)
{
    string requestUri = string.Format(baseUri, lat, lng);

    using (WebClient wc = new WebClient())
    {
        var result = wc.DownloadString(new Uri(requestUri));
        var xmlElm = XElement.Parse(result);

        var status = (from elm in xmlElm.Descendants()
              where elm.Name == "status"
              select elm).FirstOrDefault();
        if (status.Value.ToLower() == "ok")
        {
        var res = (from elm in xmlElm.Descendants()
               where elm.Name == "formatted_address"
               select elm).FirstOrDefault();
            return res.Value;
        }
        else
        {
            return "No Address Found";
        }
    }
}

Answer 2

DownloadString()方法是DownloadStringAsync()方法的同步版本。它以字符串的形式返回从服务器下载的数据。在您的代码中，您不会在任何地方读取此值。尝试使用var data = wc.DownloadString(new Uri(requestUri));获取数据。