Windows Form中通过JSON获取天气图标失败问题求助

开发C# Windows Form程序时，使用Newtonsoft JSON调用OpenWeatherMap API可正常获取温度、湿度等数据，但天气图标无法显示，无报错信息。核心代码、数据模型和测试JSON如下：

主类核心代码 #

void getweather()
{
    using (WebClient web = new WebClient())
    {
        string url = string.Format("https://api.openweathermap.org/data/2.5/weather?lat=-42.15&lon=-12.9167&appid=4ef889ce24xxxxxx4b&units=metric&cnt=6");
        var json = web.DownloadString(url);
        WeatherInfo.Root Info = JsonConvert.DeserializeObject<WeatherInfo.Root>(json);
        STRGRADOS.Text = string.Format("{0} °" + "C", Info.main.temp);
        pic_icon.ImageLocation = "https://openweathermap.org/img/w/" + Info.weather[0].icon+".PNG";
        HUMEDAD.Text = string.Format("{0}", Info.main.humidity + "%");
        Console.WriteLine(Info);
    }
}

数据模型类 #

class WeatherInfo{
 public class Weather
        {
            public int id { get; set; }
            public string main { get; set; }
            public string description { get; set; }
            public string icon { get; set; }
        }

   public class Root
        {
            public Coord coord { get; set; }
            public List<Weather> weather { get; set; }
            public string @base { get; set; }
            public Main main { get; set; }
            public int visibility { get; set; }
            public Wind wind { get; set; }
            public Clouds clouds { get; set; }
            public int dt { get; set; }
            public Sys sys { get; set; }
            public int timezone { get; set; }
            public int id { get; set; }
            public string name { get; set; }
            public int cod { get; set; }
        }
}

测试用JSON #

{"coord":{"lon":-32.9167,"lat":-12.15},"weather":[{"id":803,"main":"Clouds","description":"broken clouds","icon":"04n"}],"base":"stations","main":{"temp":25.26,"feels_like":25.64,"temp_min":25.26,"temp_max":25.26,"pressure":1018,"humidity":69,"sea_level":1018,"grnd_level":1018},"visibility":10000,"wind":{"speed":7.82,"deg":166,"gust":7.68},"clouds":{"all":79},"dt":1688501669,"sys":{"sunrise":1688459581,"sunset":1688500721},"timezone":-7200,"id":0,"name":"","cod":200}

排查出的问题 #

1. URL大小写敏感：OpenWeatherMap的图标后缀为小写.png，代码中使用的.PNG会导致部分环境下无法匹配资源。
2. 控件未强制刷新：WinForm的PictureBox设置ImageLocation后，异步加载可能未触发界面刷新。
3. 缺失模型子类：原数据模型未定义Coord、Main等子类，虽不影响已有数据获取，但存在潜在反序列化风险。
4. TLS版本兼容：OpenWeatherMap要求使用TLS 1.2及以上，部分旧环境默认TLS版本过低会导致HTTPS请求失败。

修复方案及完整示例 #

1. 修正图标URL并强制刷新控件 #

将后缀改为小写.png，设置ImageLocation后调用Refresh()强制更新界面。

2. 补充完整数据模型 #

添加缺失的Coord、Main等子类，确保反序列化完整。

3. 指定TLS版本 #

在请求前设置TLS 1.2，解决HTTPS访问问题。

4. 增加异常捕获 #

捕获请求及加载过程中的异常，便于排查问题。

修复后主类代码

void getweather()
{
    // 指定TLS版本，解决HTTPS访问限制
    System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;

    using (WebClient web = new WebClient())
    {
        string url = string.Format("https://api.openweathermap.org/data/2.5/weather?lat=-42.15&lon=-12.9167&appid=4ef889ce24xxxxxx4b&units=metric&cnt=6");
        try
        {
            var json = web.DownloadString(url);
            WeatherInfo.Root Info = JsonConvert.DeserializeObject<WeatherInfo.Root>(json);
            
            STRGRADOS.Text = string.Format("{0} °C", Info.main.temp);
            HUMEDAD.Text = string.Format("{0}%", Info.main.humidity);
            
            // 修正图标URL大小写
            string iconUrl = $"https://openweathermap.org/img/w/{Info.weather[0].icon}.png";
            pic_icon.ImageLocation = iconUrl;
            // 强制刷新控件
            pic_icon.Refresh();
            
            Console.WriteLine(Info);
        }
        catch (Exception ex)
        {
            Console.WriteLine($"加载出错：{ex.Message}");
        }
    }
}

完整数据模型类

class WeatherInfo
{
    public class Coord
    {
        public double lon { get; set; }
        public double lat { get; set; }
    }

    public class Weather
    {
        public int id { get; set; }
        public string main { get; set; }
        public string description { get; set; }
        public string icon { get; set; }
    }

    public class Main
    {
        public double temp { get; set; }
        public double feels_like { get; set; }
        public double temp_min { get; set; }
        public double temp_max { get; set; }
        public int pressure { get; set; }
        public int humidity { get; set; }
        public int sea_level { get; set; }
        public int grnd_level { get; set; }
    }

    public class Wind
    {
        public double speed { get; set; }
        public int deg { get; set; }
        public double gust { get; set; }
    }

    public class Clouds
    {
        public int all { get; set; }
    }

    public class Sys
    {
        public int sunrise { get; set; }
        public int sunset { get; set; }
    }

    public class Root
    {
        public Coord coord { get; set; }
        public List<Weather> weather { get; set; }
        public string @base { get; set; }
        public Main main { get; set; }
        public int visibility { get; set; }
        public Wind wind { get; set; }
        public Clouds clouds { get; set; }
        public int dt { get; set; }
        public Sys sys { get; set; }
        public int timezone { get; set; }
        public int id { get; set; }
        public string name { get; set; }
        public int cod { get; set; }
    }
}

额外备选方案 #

若仍无法加载，可尝试直接下载图标到内存流再加载：

// 替换原图标加载代码
string iconUrl = $"https://openweathermap.org/img/w/{Info.weather[0].icon}.png";
using (var stream = web.OpenRead(iconUrl))
{
    pic_icon.Image = Image.FromStream(stream);
}

内容的提问来源于stack exchange，提问作者jim root