Jeff Prosise has written an article “Currency Converter with ASP.NET Web Forms“, he pretty much explained how to load XML data with ASP.NET from the “Rates.xml” file. In this article I have created Currency Converter Server which can be scheduled to extract the data from third party site and build the “Rates.xml” dynamically.
CurrencyConverter.dll Component:
“CurrencyConverter.dll” This component will extract the data from PACIFIC Exchange site using regular expression patterns.
// html for which we are writing this regular expression pattern
/*
<TD align=middle>ADP</TD>
<TD align=left>Andorran Peseta</TD>
<TD align=right>100.92</TD>
<TD align=right>152.844</TD>
<TD align=right>166.386</TD>
<TD align=right>251.917</TD>
*/
Regex regex = new Regex(@”<td.*?>(.+)</td>+”, RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace);
MatchCollection matches = regex.Matches(rawHtml);
if (matches.Count > 0)
{
// Get the first match
foreach(Match match in matches)
{
if (match.Success)
{
// Get the second group in the match
Group grp = match.Groups[1];
// return data
Console.WriteLine(grp.Value);
}
}
}
Once we extract the data from the site then we can build “Rates.xml” XML file using XmlTextWriter class.
XmlTextWriter writer = new XmlTextWriter(XMLFilePath, System.Text.Encoding.UTF8);
writer.WriteStartDocument(); //Use automatic indentation for readability.
writer.Formatting = Formatting.Indented;
//Write the root element
writer.WriteStartElement(“Rates”); //Start an element
writer.WriteStartElement(“Rate”); //add sub-elements
writer.WriteElementString(“Currency”, “British Pound”);
writer.WriteElementString(“Exchange”, “0.635243”); //End the item element
writer.WriteEndElement(); // end Rate // end the root element
writer.WriteFullEndElement();
//Write the XML to file and close the writer
writer.Flush();
writer.Close();
Test file which will connect to the PACIFIC Exchange site and extract the data and build “Rates.xml” file.
class BuildXML
{
static void Main()
{ string SupplementaryExchangeRatesActualSiteUrl = “http://pacific.commerce.ubc.ca/xr/rates.html”;
Currency cc = new Currency();
cc.ExchangeRatesURL = SupplementaryExchangeRatesActualSiteUrl;
cc.XMLFilePath = “Rates.xml”;
cc.Build();
Console.WriteLine(cc.ModuleError.ToString());
}
}
PACIFIC Exchange Rate Service for 242 countries
http://pacific.commerce.ubc.ca/xr/rates.html
Here are some sites from which exchange rate data can be extracted.
PACIFIC Exchange daily Rates but limited countries
http://pacific.commerce.ubc.ca/xr/today.html
US Treasury Exchange Rates
http://www.fms.treas.gov/intn.html
Federal Reserve Bank Exchange Rates
http://www.federalreserve.gov/releases/H10/Update/
International Monetary Fund (IMF) Exchange Rates
http://www.imf.org/external/np/tre/sdr/db/rms_five.cfm
Rates.xml file:
“Rates.xml” contains 242 countries exchange rate. But if you look at the countries names they are not alphabetically sorted, I will explain this later how to sort data within ASP.NET page.
<?xml version=”1.0″ encoding=”utf-8″?>
<Rates>
<Rate>
<Currency>Andorran Peseta</Currency>
<Exchange> 154.763</Exchange>
</Rate>
<Rate>
<Currency>U.A.E. Dirham</Currency>
<Exchange> 3.673</Exchange>
</Rate>
<Rate>
<Currency>Afghanistan Afghani</Currency>
<Exchange> 42.785</Exchange>
</Rate>
<Rate>
<Currency>Albanian Lek</Currency>
<Exchange> 129.181</Exchange>
</Rate>
<Rate>
<Currency>Armenia Dram</Currency>
<Exchange> 554.882</Exchange>
</Rate>
<Rate>
<Currency>Neth. Ant. Guilder</Currency>
<Exchange> 1.78</Exchange>
</Rate>
<Rate>
<Currency>Angolan Kwanza</Currency>
<Exchange> 65.0163</Exchange>
</Rate>
<Rate>
<Currency>Argentine Peso</Currency>
<Exchange> 3.155</Exchange>
</Rate>
<Rate>
<Currency>Austrian Schilling</Currency>
<Exchange> 12.7991</Exchange>
</Rate>
<Rate>
<Currency>Christmas Is. Dollar</Currency>
<Exchange> 1.65399</Exchange>
</Rate>
<Rate>
<Currency>Cocos(Keeling) Is.</Currency>
<Exchange> 1.65399</Exchange>
</Rate>
.
.
.
.
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Compiling and building your Component:
Zip file contains “CurrencyConverter.cs”, “BuildXML.cs”, and “CurrencyConverter.aspx”. And I have also included compile.bat, rate.make, and Rates.xml. By running the compile.bat file at the command prompt it will create “CurrencyConverter.dll” component and it will also build “BuildXML.exe” file, by executing the “BuildXML.exe” at the command prompt it will connect to PACIFIC Exchange site and extract the data and build us “Rates.xml” file. Which can then be read by our asp.net page “Converter.aspx” in a browser. Converter.aspx ASP.NET page explanation:
Jeff Prosise pretty much explain this portion of the asp.net page in his article. Earlier I mentioned that “Rates.xml” file data is not sorted. To sort the Country names in the ListBox is easy. Once we fill the DataView then we can use Sort property of the DataView Class to sort the data in the ListBox control.
<%@ Page Language=”C#” %>
<%@ Import Namespace=System.Data %> <script runat=”server”> void Page_Load(object sender, System.EventArgs e)
{
// If this isn’t a postback, initialize the ListBox
if (!IsPostBack)
{
DataSet ds = new DataSet();
ds.ReadXml(Server.MapPath (“Rates.xml”));
DataView dv = ds.Tables[0].DefaultView;
dv.Sort = “Currency ASC”;
lstboxCurrency.DataSource = dv;
lstboxCurrency.SelectedIndex = 0;
lstboxCurrency.DataTextField = “Currency”;
lstboxCurrency.DataBind();
}
}
// Perform the conversion and display the results
void btnConvert_Click(object sender, System.EventArgs e)
{
try
{
DataSet ds = new DataSet();
ds.ReadXml(Server.MapPath(“Rates.xml”));
DataRow[] rows = ds.Tables[0].Select(“Currency = ‘” + lstboxCurrency.SelectedItem.Text + “‘”);
decimal CurrencyAmount = Convert.ToDecimal(Amount.Text);
decimal rate = Convert.ToDecimal(rows[0][“Exchange”]);
decimal amount = CurrencyAmount * rate;
Result.Text = amount.ToString(“f2”);
}
catch (FormatException)
{
Errors.Text = “Error”;
}
} void Page_Init (Object sender, EventArgs e)
{
// Wire the Convert button to OnConvert
btnConvert.Click += new System.EventHandler(btnConvert_Click);
Load += new System.EventHandler(Page_Load);
}
</script>
ASP.NET page output:
Note:
In this article PACIFIC Exchange Rate Service data is strictly used for educational purpose only and should not be used in any commercial application.
Reference:
A Web Forms Currency Converter
http://webdeveloper.earthweb.com/webjs/print.php/10959_982451_5
get the source code: CurrencyConverter.zip
Originally published by CSharpHelp
Waheed Khan is currently working with ASP.NET, ADO.NET, XML, and C#
