WEBCLIENT to “European Central Bank” to calculated Exchange between countries.

• Download source code - 19.6 Kb

Introduction

The ECB very conveniently (and for free) gives daily the exchange rates of the most

common currencies, in several file formats, among which an XML file for parsing. (Shortened copy below)

<?xml version="1.0" encoding="UTF-8"?>
<gesmes:Envelope xmlns:gesmes="http://www.gesmes.org/xml/2002-08-01" xmlns="http://www.ecb.int/vocabulary/2002-08-01/eurofxref">
<gesmes:subject>Reference rates</gesmes:subject>
<gesmes:Sender>
<gesmes:name>European Central Bank</gesmes:name>
</gesmes:Sender>
<Cube>
<Cube time='2004-03-11'>
<Cube currency='USD' rate='1.2256'/>
<Cube currency='JPY' rate='135.58'/>
<Cube currency='DKK' rate='7.4518'/>
....
<Cube currency='ZAR' rate='8.2441'/>
</Cube>
</Cube>
</gesmes:Envelope>

Since this is a free resource, then this allow me to post also the URI for the XML file:
http://www.ecb.int/stats/eurofxref/eurofxref-hist.xml

I will make a Windows Application there was working as a Web Client to "ECB" XML.

From real rate of exchange from European Central Bank making a calculator to calculated the rate of Exchange between difference countries.

Background

The basic ideas are to get make a program to calculated the rate between difference countries. The European Central Bank dispose the a XML file over the typical

trade countries exchange rate. From this I can calculated how many money I have to pay for a product. Just remember, that we can only get the

exchange rate for the actual day when Bank is closed about 4 o'clock.

Using the code

Microsoft working with an XmlTextReader there can read from any kind of XML file.

But the ECB xml file is not a real web services so I want to parse it to a Dataset descript se below.

On this side http://www.oanda.com/site/help/iso_code.shtml can the index lists currency ISO codes by

country and precious metal. You can also find an ISO currency code by code. See picture how Web Client works.

I Store the parsing data into a dataset, see picture.

From this dataset I can find and get data, so on.

Code

private ExchanceRate parseWebXML(string WebAddress)
{
	XmlTextReader xmlReader;

	ExchanceRate dsVa = new ExchanceRate();

	DataRow newRowVa = null;

	try
	{
		//Read data from the XML-file over the interNET
		xmlReader = new XmlTextReader(WebAddress);
	}
	catch( WebException )
	{
		throw new WebException("There has been a mistake with collect the xmlfile from the net!");
	}

	try
	{
		while( xmlReader.Read() )
		{
			if (xmlReader.Name != "")
			{
				//Check that there are node call gesmes:name
				if (xmlReader.Name == "gesmes:name") 
				{
					_author = xmlReader.ReadString();
				}
						
				for (int i = 0 ; i < xmlReader.AttributeCount; i++)
				{
					//Check that there are node call Cube
					if (xmlReader.Name == "Cube") 
					{
						//Check that there are 1 attribut, then get the date
						if (xmlReader.AttributeCount == 1)
						{
							xmlReader.MoveToAttribute("time");

							DateTime tim = DateTime.Parse(xmlReader.Value);
							newRowVa = null;
							DataRow newRowCo = null;

							newRowVa = dsVa.Exchance.NewRow();
							newRowVa["Date"]= tim;
							dsVa.Exchance.Rows.Add(newRowVa);

							newRowCo = dsVa.Country.NewRow();
							newRowCo["Initial"]= "EUR";
							newRowCo["Name"]= convert.MoneyName("EUR");		// Find Country name from ISO code
							newRowCo["Rate"]= 1.0;
							dsVa.Country.Rows.Add(newRowCo);

							newRowCo.SetParentRow(newRowVa);	// Make Key to subtable
						}

						//If the number of attributs are 2, so get the ExchangeRate-node
						if (xmlReader.AttributeCount == 2)
						{
							xmlReader.MoveToAttribute("currency");
							string cur = xmlReader.Value;
                  
							xmlReader.MoveToAttribute("rate");
							decimal rat = decimal.Parse(xmlReader.Value.Replace(".",",")); // I am using "," as a decimal symbol

							DataRow newRowCo = null;

							newRowCo = dsVa.Country.NewRow();
							newRowCo["Initial"]= cur;
							newRowCo["Name"]= convert.MoneyName(cur);
							newRowCo["Rate"]= rat;
							dsVa.Country.Rows.Add(newRowCo);

							newRowCo.SetParentRow(newRowVa);	
						}

					xmlReader.MoveToNextAttribute();
				}
			}
		}
	}
	catch( WebException )
	{
		throw new WebException("connections lost");
	}

	return dsVa;
}

Here I can calculated the Exchange between difference countries from the Exchange rate.

private static double ExRateValue(double Input, double FromContry, double ToContry)
{
	double result = 0;
	if( FromContry == 0 ) return 0;
	result = (Input/FromContry)*ToContry;
	result = Math.Round(result,2);

	return result;
}

Conclusion

In this article has been shown one simple way how to implement a solution for connecting over Internet.

I used the power of .Net Technologies such as Web client in the XmlTextReader.

Remember that using this link it get data back from start of the Europe Central Bank history 01/04/1999,

and on mine computer it take ½ second to load the xml and parse the data to mine dataset.

Good luck.