C# Get Current Exchange Rate from XE

I need to display current exchange rates on my application.
Is it possible to retrieve the exchange rate from http://www.xe.com (XE Converter)
Here what I tried:

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;
        }

With this code I am not having the full output... the decimal part is not
showing...

Yes XE offers an API but it is paid only. Making an automated tool to extract the data is not allowed. (source)

I tried your code and it is working for me. What do you exactly mean with the decimal part is not showing ?

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");
    }
}

TestCode:

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

Result:

$ 5 = € 4,661
£ 20 = $ 25,616

EDIT

Get Newtonsoft.Json using NuGet

PM> Install-Package Newtonsoft.Json

Code:

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();
        }
    }