C# 从 XE 获取当前汇率

Question

我需要在我的应用程序上显示当前汇率。
是否可以从http://www.xe.com 检索汇率（XE 转换器）
这是我尝试过的：

public string CurrencyConversion(decimal amount, string fromCurrency, string toCurrency)
        {
            string Output = "";
             string fromCurrency1 = comboBox1.Text;
             string toCurrency1 = comboBox2.Text;
             decimal amount1 = Convert.ToDecimal(textBox1.Text);

            // For other currency symbols see http://finance.yahoo.com/currency-converter/
            // Construct URL to query the Yahoo! Finance API

            const string urlPattern = "http://finance.yahoo.com/d/quotes.csv?s={0}{1}=X&f=l1";
            string url = string.Format(urlPattern, fromCurrency1, toCurrency1);

            // Get response as string
            string response = new WebClient().DownloadString(url);

            // Convert string to number
            decimal exchangeRate =
                decimal.Parse(response, System.Globalization.CultureInfo.InvariantCulture);

            // Output the result
            Output = (amount1 * exchangeRate).ToString();
            textBox2.Text = Output;

            return Output;
        }

使用此代码，我没有完整的输出...小数部分没有
显示...

Answer 1

是的，XE 提供API，但它只需要付费。 不允许制作自动化工具来提取数据。 (source)

我试过你的代码，它对我有用。 the decimal part is not showing 到底是什么意思？

public string CurrencyConversion(decimal amount, string fromCurrency, string toCurrency)
{
    string url = string.Format(urlPattern, fromCurrency, toCurrency);

    using (var wc = new WebClient())
    {
        var response = wc.DownloadString(url);
        decimal exchangeRate = decimal.Parse(response, CultureInfo.InvariantCulture);

        return (amount * exchangeRate).ToString("N3");
    }
}

测试代码：

Console.WriteLine($"$ 5 = € {CurrencyConversion(5m, "USD", "EUR")}");
Console.WriteLine($"£ 20 = $ {CurrencyConversion(20m, "GBP", "USD")}");

结果：

$ 5 = € 4,661
£ 20 = $ 25,616

编辑

使用 NuGet 获取 Newtonsoft.Json

PM> Install-Package Newtonsoft.Json

代码：

private const string urlPattern = "http://rate-exchange-1.appspot.com/currency?from={0}&to={1}";
    public string CurrencyConversion(decimal amount, string fromCurrency, string toCurrency)
    {
        string url = string.Format(urlPattern, fromCurrency, toCurrency);

        using (var wc = new WebClient())
        {
            var json = wc.DownloadString(url);

            Newtonsoft.Json.Linq.JToken token = Newtonsoft.Json.Linq.JObject.Parse(json);
            decimal exchangeRate = (decimal)token.SelectToken("rate");

            return (amount * exchangeRate).ToString();
        }
    }