我的代码不断抛出我的 catch 异常，我不知道为什么

Question

我正在创建一个使用 API 访问密钥来获取股票数据信息的项目。用户输入股票代码，然后点击一个按钮，然后加载所有股票信息。但是，当输入正确的股票代码并单击按钮加载信息时，它会不断抛出我设置的 catch 异常，我不知道为什么。我以前从未使用过 try catch，所以我做错了什么吗？

这是我在SettingsTab.cs 中尝试获取股票信息的方法：

async void AddStockButton_Clicked(object sender, EventArgs e)
        {
            string symbol = symbolEntry.Text.ToLower();
            //Create a try catch block to make sure the symbol exists and isn't already added in the list
            try
            {
                //Create new data manager and pass in the users chosen symbol
                DataManager dataManager = new DataManager(symbol);
                StockData newStockData = await dataManager.GetStock();
            if (stockList.Contains(newStockData))
            {
                //If stock does not exists or is a duplicate, display error alert
                //Change success label text to Unsuccessful, change color to red, & make visible
                await DisplayAlert("DUPLICATE STOCK", "This stock is already added to your favorites!", "OKAY");
                successLabel.Text = "Unsuccessful due to duplicate";
                successLabel.TextColor = Color.Red;
                successLabel.IsVisible = true;
            }
            else if (!stockList.Contains(newStockData))
            {
                //If stock exists and not duplicate, add that stock to a list of stockData
                //Display success alert
                //Make success label visible
                stockList.Add(newStockData);
                await DisplayAlert("STOCK ADDED", "This stock has been successfully added to your favorites!", "OKAY");
                successLabel.IsVisible = true;

                MessagingCenter.Send<StockData>(newStockData, "NewStockData");
            }

            }
            catch (WebException ex)
            {
                await DisplayAlert("API FAILED","Unable to retrieve data for that symbol. Please check that you typed it correctly or try again later.", "GO BACK");
                successLabel.Text = "Unsuccessful due to API error";
                successLabel.TextColor = Color.Red;
                successLabel.IsVisible = true;
            }
        }

这是我的 DataManager.cs 类，它获取 API 并将其转换为 json：

public class DataManager
    {
        //This class will be responsible for pulling data from remote API
        //And putting it into the stock data opjects and passing it back to normal UI classes
        //Create variables to use
        WebClient apiConnection = new WebClient();
        //Create a string to start API
        string startAPI = "http://api.marketstack.com/v1/eod/latest?accesskey=<<ACCESS KEY REDACTED>>";
        string Symbols { get; set; }
        
        string ApiEndPoint
        {
            get
            {
                return startAPI + Symbols;
            }
        }

        public DataManager(string symbolsToDownload)
        {
            //make symbols equal to whatever gets passed in
            Symbols = symbolsToDownload;
        }

        public async Task<StockData> GetStock()
        {
            //Create a string representation of the downloaded data from ApiEndPoint
            string apiString = await apiConnection.DownloadStringTaskAsync(ApiEndPoint);

            //Create a JObject to store the apiString as a parsed JObject to get access
            //to the json formatted data
            JObject jsonData = JObject.Parse(apiString);

            //create another JObject
            JObject firstStock = (JObject)jsonData["data"][0];

            Debug.WriteLine(firstStock.ToString());

            //Create a new StockData object
            StockData stockData = new StockData();
            stockData.StockName = firstStock["symbol"].ToString();
            //We need to get the string value and parse it as a Double to define the stock Data property
            stockData.OpenPrice = Double.Parse(firstStock["open"].ToString());
            stockData.ClosePrice = Double.Parse(firstStock["close"].ToString());
            stockData.HighPrice = Double.Parse(firstStock["high"].ToString());
            stockData.LowPrice = Double.Parse(firstStock["low"].ToString());
            stockData.Volume = Double.Parse(firstStock["adj_volume"].ToString());
            stockData.Exchange = firstStock["exchange"].ToString();
            stockData.TradingDay = DateTime.Parse(firstStock["open"].ToString());

            //return the new stock data object
            return stockData;
        }
    }

我只是在使用我的 try catch 错误的方式吗？我在网上找到的所有东西都让我感到困惑。我仍然是一名学生并且正在学习，所以如果这是一个愚蠢的问题，我深表歉意。请帮帮我

Answer 1

如果您将网址粘贴到浏览器中

string startAPI = "http://api.marketstack.com/v1/eod/latest?accesskey=<<ACCESS KEY REDACTED>>&symbol=AAPL";

你会得到这个非常友好和明确的错误信息

{
  "error":
  {
    "code": "missing_access_key",
    "message": "You have not supplied an API Access Key. [Required format: access_key=YOUR_ACCESS_KEY]"
  }
}

accesskey 应该是access_key

Answer 2

1. 确保access_key的值传输正确且值正确。
2. 在try的第一行添加断点，看看哪里出错了。
3. 打印出catch中的“ex”，查看错误的具体信息。