In this article I will explain how to get the Convert Amount from one Currency to another using the latest Currency Exchange Rates from Google API in ASP.Net
 
HTML Markup
The HTML Markup consist of a TextBox for entering the amount, two DropDownLists for selecting the Currencies and a Button for converting the Currency
<asp:TextBox ID = "txtAmount" runat = "server" Text = "100"></asp:TextBox>
<asp:DropDownList ID="ddlFrom" runat="server">
    <asp:ListItem Value="USD" Selected = "true" Text="United States Dollars $"></asp:ListItem>
    <asp:ListItem Value="EUR" Text="Euro €"></asp:ListItem>
    <asp:ListItem Value="GBP" Text="United Kingdom Pounds £"></asp:ListItem>
    <asp:ListItem Value="JPY" Text="Japan Yen ¥"></asp:ListItem>
    <asp:ListItem Value="AFN" Text="Afghanistan Afghanis ؋"></asp:ListItem>
    <asp:ListItem Value="ALL" Text="Albania Leke Lek"></asp:ListItem>
    <asp:ListItem Value="DZD" Text="Algeria Dinars DA"></asp:ListItem>
    <asp:ListItem Value="ARS" Text="Argentina Pesos $"></asp:ListItem>
    <asp:ListItem Value="AUD" Text="Australia Dollars $"></asp:ListItem>
    <asp:ListItem Value="BSD" Text="Bahamas Dollars $"></asp:ListItem>
    <asp:ListItem Value="BHD" Text="Bahrain Dinars BD"></asp:ListItem>
    <asp:ListItem Value="BDT" Text="Bangladesh Taka Tk"></asp:ListItem>
    <asp:ListItem Value="BBD" Text="Barbados Dollars $"></asp:ListItem>
    <asp:ListItem Value="BMD" Text="Bermuda Dollars $"></asp:ListItem>
    <asp:ListItem Value="BRL" Text="Brazil Reais R$"></asp:ListItem>
   <asp:ListItem Value="BGN" Text="Bulgaria Leva лв"></asp:ListItem>
    <asp:ListItem Value="CAD" Text="Canada Dollars $"></asp:ListItem>
    <asp:ListItem Value="XOF" Text="CFA Francs BCEAO CFAF"></asp:ListItem>
    <asp:ListItem Value="XAF" Text="CFA Francs BEAC CFAF"></asp:ListItem>
    <asp:ListItem Value="XPF" Text="CFP Francs "></asp:ListItem>
    <asp:ListItem Value="CLP" Text="Chile Pesos $"></asp:ListItem>
    <asp:ListItem Value="CNY" Text="China Yuan Renminbi 元"></asp:ListItem>
    <asp:ListItem Value="COP" Text="Colombia Pesos $"></asp:ListItem>
    <asp:ListItem Value="CRC" Text="Costa Rica Colones ₡"></asp:ListItem>
    <asp:ListItem Value="HRK" Text="Croatia Kuna kn"></asp:ListItem>
    <asp:ListItem Value="CYP" Text="Cyprus Pounds £"></asp:ListItem>
    <asp:ListItem Value="CZK" Text="Czech Republic Koruny Kč"></asp:ListItem>
    <asp:ListItem Value="DKK" Text="Denmark Kroner kr"></asp:ListItem>
    <asp:ListItem Value="DOP" Text="Dominican Republic Pesos RD$"></asp:ListItem>
    <asp:ListItem Value="XCD" Text="East Caribbean Dollars $"></asp:ListItem>
    <asp:ListItem Value="EGP" Text="Egypt Pounds £"></asp:ListItem>
    <asp:ListItem Value="EEK" Text="Estonia Krooni kr"></asp:ListItem>
    <asp:ListItem Value="FJD" Text="Fiji Dollars $"></asp:ListItem>
    <asp:ListItem Value="HKD" Text="Hong Kong Dollars 元"></asp:ListItem>
    <asp:ListItem Value="HUF" Text="Hungary Forint Ft"></asp:ListItem>
    <asp:ListItem Value="ISK" Text="Iceland Kronur kr"></asp:ListItem>
    <asp:ListItem Value="XDR" Text="IMF Special Drawing Rights "></asp:ListItem>
    <asp:ListItem Value="INR" Text="India Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="IDR" Text="Indonesia Rupiahs Rp"></asp:ListItem>
    <asp:ListItem Value="IRR" Text="Iran Rials ﷼"></asp:ListItem>
    <asp:ListItem Value="IQD" Text="Iraq Dinars ID"></asp:ListItem>
    <asp:ListItem Value="ILS" Text="Israel New Shekels ₪"></asp:ListItem>
    <asp:ListItem Value="JMD" Text="Jamaica Dollars J$"></asp:ListItem>
    <asp:ListItem Value="JOD" Text="Jordan Dinars JD"></asp:ListItem>
    <asp:ListItem Value="KZT" Text="Kazakhstan Tenge лв"></asp:ListItem>
    <asp:ListItem Value="KES" Text="Kenya Shillings K Sh"></asp:ListItem>
    <asp:ListItem Value="KWD" Text="Kuwait Dinars KD"></asp:ListItem>
    <asp:ListItem Value="LBP" Text="Lebanon Pounds £"></asp:ListItem>
    <asp:ListItem Value="MYR" Text="Malaysia Ringgits RM"></asp:ListItem>
    <asp:ListItem Value="MTL" Text="Malta Liri Lm"></asp:ListItem>
    <asp:ListItem Value="MUR" Text="Mauritius Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="MXN" Text="Mexico Pesos $"></asp:ListItem>
    <asp:ListItem Value="MAD" Text="Morocco Dirhams DH"></asp:ListItem>
    <asp:ListItem Value="NZD" Text="New Zealand Dollars $"></asp:ListItem>
    <asp:ListItem Value="NGN" Text="Nigeria Nairas ₦"></asp:ListItem>
    <asp:ListItem Value="NOK" Text="Norway Kroner kr"></asp:ListItem>
    <asp:ListItem Value="OMR" Text="Oman Rials ﷼"></asp:ListItem>
    <asp:ListItem Value="PKR" Text="Pakistan Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="XPD" Text="Palladium Ounces "></asp:ListItem>
    <asp:ListItem Value="PEN" Text="Peru Nuevos Soles S/."></asp:ListItem>
    <asp:ListItem Value="PHP" Text="Philippines Pesos Php"></asp:ListItem>
    <asp:ListItem Value="PLN" Text="Poland Zlotych zł"></asp:ListItem>
    <asp:ListItem Value="QAR" Text="Qatar Riyals ﷼"></asp:ListItem>
    <asp:ListItem Value="RON" Text="Romania New Lei lei"></asp:ListItem>
    <asp:ListItem Value="RUB" Text="Russia Rubles руб"></asp:ListItem>
    <asp:ListItem Value="SAR" Text="Saudi Arabia Riyals ﷼"></asp:ListItem>
    <asp:ListItem Value="XAG" Text="Silver Ounces "></asp:ListItem>
    <asp:ListItem Value="SGD" Text="Singapore Dollars $"></asp:ListItem>
    <asp:ListItem Value="ZAR" Text="South Africa Rand R"></asp:ListItem>
    <asp:ListItem Value="KRW" Text="South Korea Won ₩"></asp:ListItem>
    <asp:ListItem Value="LKR" Text="Sri Lanka Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="SDG" Text="Sudan Pounds "></asp:ListItem>
    <asp:ListItem Value="SEK" Text="Sweden Kronor kr"></asp:ListItem>
    <asp:ListItem Value="CHF" Text="Switzerland Francs CHF"></asp:ListItem>
    <asp:ListItem Value="TWD" Text="Taiwan New Dollars NT$"></asp:ListItem>
    <asp:ListItem Value="THB" Text="Thailand Baht ฿"></asp:ListItem>
    <asp:ListItem Value="TTD" Text="Trinidad and Tobago Dollars TT$"></asp:ListItem>
    <asp:ListItem Value="TND" Text="Tunisia Dinars TD"></asp:ListItem>
    <asp:ListItem Value="TRY" Text="Turkey Lira YTL"></asp:ListItem>
    <asp:ListItem Value="AED" Text="United Arab Emirates Dirhams Dh"></asp:ListItem>
    <asp:ListItem Value="VEF" Text="Venezuela Bolivares Fuertes "></asp:ListItem>
    <asp:ListItem Value="VND" Text="Vietnam Dong ₫"></asp:ListItem>
    <asp:ListItem Value="ZMK" Text="Zambia Kwacha ZK"></asp:ListItem>
</asp:DropDownList>
to
    <asp:DropDownList ID="ddlTo" runat="server">
    <asp:ListItem Value="USD" Text="United States Dollars $"></asp:ListItem>
    <asp:ListItem Value="EUR" Text="Euro €"></asp:ListItem>
    <asp:ListItem Value="GBP" Text="United Kingdom Pounds £"></asp:ListItem>
    <asp:ListItem Value="JPY" Text="Japan Yen ¥"></asp:ListItem>
    <asp:ListItem Value="AFN" Text="Afghanistan Afghanis ؋"></asp:ListItem>
    <asp:ListItem Value="ALL" Text="Albania Leke Lek"></asp:ListItem>
    <asp:ListItem Value="DZD" Text="Algeria Dinars DA"></asp:ListItem>
    <asp:ListItem Value="ARS" Text="Argentina Pesos $"></asp:ListItem>
    <asp:ListItem Value="AUD" Text="Australia Dollars $"></asp:ListItem>
    <asp:ListItem Value="BSD" Text="Bahamas Dollars $"></asp:ListItem>
    <asp:ListItem Value="BHD" Text="Bahrain Dinars BD"></asp:ListItem>
    <asp:ListItem Value="BDT" Text="Bangladesh Taka Tk"></asp:ListItem>
    <asp:ListItem Value="BBD" Text="Barbados Dollars $"></asp:ListItem>
    <asp:ListItem Value="BMD" Text="Bermuda Dollars $"></asp:ListItem>
    <asp:ListItem Value="BRL" Text="Brazil Reais R$"></asp:ListItem>
    <asp:ListItem Value="BGN" Text="Bulgaria Leva лв"></asp:ListItem>
    <asp:ListItem Value="CAD" Text="Canada Dollars $"></asp:ListItem>
    <asp:ListItem Value="XOF" Text="CFA Francs BCEAO CFAF"></asp:ListItem>
    <asp:ListItem Value="XAF" Text="CFA Francs BEAC CFAF"></asp:ListItem>
    <asp:ListItem Value="XPF" Text="CFP Francs "></asp:ListItem>
    <asp:ListItem Value="CLP" Text="Chile Pesos $"></asp:ListItem>
    <asp:ListItem Value="CNY" Text="China Yuan Renminbi 元"></asp:ListItem>
    <asp:ListItem Value="COP" Text="Colombia Pesos $"></asp:ListItem>
    <asp:ListItem Value="CRC" Text="Costa Rica Colones ₡"></asp:ListItem>
    <asp:ListItem Value="HRK" Text="Croatia Kuna kn"></asp:ListItem>
    <asp:ListItem Value="CYP" Text="Cyprus Pounds £"></asp:ListItem>
    <asp:ListItem Value="CZK" Text="Czech Republic Koruny Kč"></asp:ListItem>
    <asp:ListItem Value="DKK" Text="Denmark Kroner kr"></asp:ListItem>
    <asp:ListItem Value="DOP" Text="Dominican Republic Pesos RD$"></asp:ListItem>
    <asp:ListItem Value="XCD" Text="East Caribbean Dollars $"></asp:ListItem>
    <asp:ListItem Value="EGP" Text="Egypt Pounds £"></asp:ListItem>
    <asp:ListItem Value="EEK" Text="Estonia Krooni kr"></asp:ListItem>
    <asp:ListItem Value="FJD" Text="Fiji Dollars $"></asp:ListItem>
    <asp:ListItem Value="HKD" Text="Hong Kong Dollars 元"></asp:ListItem>
    <asp:ListItem Value="HUF" Text="Hungary Forint Ft"></asp:ListItem>
    <asp:ListItem Value="ISK" Text="Iceland Kronur kr"></asp:ListItem>
    <asp:ListItem Value="XDR" Text="IMF Special Drawing Rights "></asp:ListItem>
    <asp:ListItem Value="INR" Selected = "True" Text="India Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="IDR" Text="Indonesia Rupiahs Rp"></asp:ListItem>
    <asp:ListItem Value="IRR" Text="Iran Rials ﷼"></asp:ListItem>
    <asp:ListItem Value="IQD" Text="Iraq Dinars ID"></asp:ListItem>
    <asp:ListItem Value="ILS" Text="Israel New Shekels ₪"></asp:ListItem>
    <asp:ListItem Value="JMD" Text="Jamaica Dollars J$"></asp:ListItem>
    <asp:ListItem Value="JOD" Text="Jordan Dinars JD"></asp:ListItem>
    <asp:ListItem Value="KZT" Text="Kazakhstan Tenge лв"></asp:ListItem>
    <asp:ListItem Value="KES" Text="Kenya Shillings K Sh"></asp:ListItem>
    <asp:ListItem Value="KWD" Text="Kuwait Dinars KD"></asp:ListItem>
    <asp:ListItem Value="LBP" Text="Lebanon Pounds £"></asp:ListItem>
    <asp:ListItem Value="MYR" Text="Malaysia Ringgits RM"></asp:ListItem>
    <asp:ListItem Value="MTL" Text="Malta Liri Lm"></asp:ListItem>
    <asp:ListItem Value="MUR" Text="Mauritius Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="MXN" Text="Mexico Pesos $"></asp:ListItem>
    <asp:ListItem Value="MAD" Text="Morocco Dirhams DH"></asp:ListItem>
    <asp:ListItem Value="NZD" Text="New Zealand Dollars $"></asp:ListItem>
    <asp:ListItem Value="NGN" Text="Nigeria Nairas ₦"></asp:ListItem>
    <asp:ListItem Value="NOK" Text="Norway Kroner kr"></asp:ListItem>
    <asp:ListItem Value="OMR" Text="Oman Rials ﷼"></asp:ListItem>
    <asp:ListItem Value="PKR" Text="Pakistan Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="XPD" Text="Palladium Ounces "></asp:ListItem>
    <asp:ListItem Value="PEN" Text="Peru Nuevos Soles S/."></asp:ListItem>
    <asp:ListItem Value="PHP" Text="Philippines Pesos Php"></asp:ListItem>
    <asp:ListItem Value="PLN" Text="Poland Zlotych zł"></asp:ListItem>
    <asp:ListItem Value="QAR" Text="Qatar Riyals ﷼"></asp:ListItem>
    <asp:ListItem Value="RON" Text="Romania New Lei lei"></asp:ListItem>
    <asp:ListItem Value="RUB" Text="Russia Rubles руб"></asp:ListItem>
    <asp:ListItem Value="SAR" Text="Saudi Arabia Riyals ﷼"></asp:ListItem>
    <asp:ListItem Value="XAG" Text="Silver Ounces "></asp:ListItem>
    <asp:ListItem Value="SGD" Text="Singapore Dollars $"></asp:ListItem>
    <asp:ListItem Value="ZAR" Text="South Africa Rand R"></asp:ListItem>
    <asp:ListItem Value="KRW" Text="South Korea Won ₩"></asp:ListItem>
    <asp:ListItem Value="LKR" Text="Sri Lanka Rupees ₨"></asp:ListItem>
    <asp:ListItem Value="SDG" Text="Sudan Pounds "></asp:ListItem>
    <asp:ListItem Value="SEK" Text="Sweden Kronor kr"></asp:ListItem>
    <asp:ListItem Value="CHF" Text="Switzerland Francs CHF"></asp:ListItem>
    <asp:ListItem Value="TWD" Text="Taiwan New Dollars NT$"></asp:ListItem>
    <asp:ListItem Value="THB" Text="Thailand Baht ฿"></asp:ListItem>
    <asp:ListItem Value="TTD" Text="Trinidad and Tobago Dollars TT$"></asp:ListItem>
    <asp:ListItem Value="TND" Text="Tunisia Dinars TD"></asp:ListItem>
    <asp:ListItem Value="TRY" Text="Turkey Lira YTL"></asp:ListItem>
    <asp:ListItem Value="AED" Text="United Arab Emirates Dirhams Dh"></asp:ListItem>
    <asp:ListItem Value="VEF" Text="Venezuela Bolivares Fuertes "></asp:ListItem>
    <asp:ListItem Value="VND" Text="Vietnam Dong ₫"></asp:ListItem>
    <asp:ListItem Value="ZMK" Text="Zambia Kwacha ZK"></asp:ListItem>
</asp:DropDownList>
<asp:Button ID="btnConvert" runat="server" Text="Convert" OnClick = "Convert" />
 
 
Namespaces
You will need to import the following namespaces
C#
using System.Net;
using System.Web.Script.Serialization;
 
VB.Net
Imports System.Net
Imports System.Web.Script.Serialization
 
 
Class to hold to the Currency Conversion Values
Since the Google API returns the Currency Conversion rates in JSON format, we’ll have to make use of a Class to convert the JSON string to C# object using JavaScriptSerializer.
C#
public class Rate
{
    public string to { get; set; }
    public string from { get; set; }
    public double rate { get; set; }
}
 
VB.Net
Public Class Rate
    Public Property [to]() As String
        Get
            Return _to
        End Get
        Set(value As String)
            _to = value
        End Set
    End Property
    Private _to As String
    Public Property from() As String
        Get
            Return _from
        End Get
        Set(value As String)
            _from = value
        End Set
    End Property
    Private _from As String
    Public Property rate() As Double
        Get
            Return _rate
        End Get
        Set(value As Double)
            _rate = value
        End Set
    End Property
    Private _rate As Double
End Class
 
 
Converting Amount Value from one Currency to another using Currency Exchange Rates
On the click of the Convert Button a call is made to the Google Exchange API using WebClient class with the From Currency i.e. the Current Currency and the To Currency i.e. the Currency you want to convert.
The Service then returns a JSON string which contains the Current Exchange Rate as per the market.
Now the exchange rate is multiplied with the amount to get the Converted Amount Value.
C#
protected void Convert(object sender, EventArgs e)
{
    double amount = 0d;
    if (double.TryParse(txtAmount.Text.Trim(), out amount))
    {
        string url = string.Format("http://rate-exchange.appspot.com/currency?from={0}&to={1}", ddlFrom.SelectedItem.Value, ddlTo.SelectedItem.Value);
        WebClient client = new WebClient();
        string rates = client.DownloadString(url);
        Rate rate = new JavaScriptSerializer().Deserialize<Rate>(rates);
        double converted_amount = amount * rate.rate;
        string message = ddlFrom.SelectedItem.Value + ": " + amount + "\\n";
        message += ddlTo.SelectedItem.Value + ": " + converted_amount + "\\n";
        message += "Rate: 1 " + ddlFrom.SelectedItem.Value + " = " + rate.rate + " " + ddlTo.SelectedItem.Value;
        ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('" + message + "');", true);
    }
    else
    {
        ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Invalid amount value.');", true);
    }
}
 
VB.Net
Protected Sub Convert(sender As Object, e As EventArgs)
    Dim amount As Double = 0.0
    If Double.TryParse(txtAmount.Text.Trim(), amount) Then
        Dim url As String = String.Format("http://rate-exchange.appspot.com/currency?from={0}&to={1}", ddlFrom.SelectedItem.Value, ddlTo.SelectedItem.Value)
        Dim client As New WebClient()
        Dim rates As String = client.DownloadString(url)
        Dim rate As Rate = New JavaScriptSerializer().Deserialize(Of Rate)(rates)
        Dim converted_amount As Double = amount * rate.rate
        Dim message As String = ddlFrom.SelectedItem.Value & ": " & amount & "\n"
        message &= ddlTo.SelectedItem.Value & ": " & converted_amount & "\n"
        message &= "Rate: 1 " & ddlFrom.SelectedItem.Value & " = " & rate.rate & " " & ddlTo.SelectedItem.Value
        ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('" & message & "');", True)
    Else
        ClientScript.RegisterStartupScript(Me.[GetType](), "alert", "alert('Invalid amount value.');", True)
    End If
End Sub
 
Currency Conversion as per Exchange Rates using Google API Web Service in ASP.Net

Currency Conversion as per Exchange Rates using Google API Web Service in ASP.Net
 
Demo
View Demo
 
Downloads