//calculate exchanged rate
public double CalculateExchangedRate(string currencyCross, string currency, double amount)
{
#region CalculateExchangedRate sanity
//throw exception if currencyCross is empty,
//whitespace, or otherwise not 6 characters
if (String.IsNullOrWhiteSpace(currencyCross) || currency.Length != 6)
{
throw new ArgumentException("Currency cross must be exactly six characters.");
}
//throw exception if currencyCross does not match an entry in CurrencyCrosses
if (!CurrencyCrosses.Contains(currencyCross))
{
throw new ArgumentException("Given currency cross does not exist.");
}
//throw exception if currency does not match an entry in Currencies
if (!Currencies.Contains(currency))
{
throw new ArgumentException("Given currency does not exist.");
}
//throw exception if there is no exchange rate for currencyCross
if (!ExchangeRates.ContainsKey(currencyCross))
{
throw new ArgumentException("Given currency cross does not have a specified exchange rate.");
}
//throw exception if amount is not positive
if (amount <= 0)
{
throw new ArgumentException("Amount must be positive.");
}
#endregion
double rate = ExchangeRates[currencyCross];
if (currencyCross.Substring(0, 3) == currency) //if they want the first currency of the cross currency (AAA from AAABBB),
{
amount *= rate; //multiply amount by rate
return(amount); //and return amount
}
else //ELSE
{
double reverseRate = 1 / rate; //reverse the rate (if 1 AAA = 6.50 BBB, 1 BBB = 1 / 6.50 = 0.15 AAA),
amount *= reverseRate; //multiply amount by reversed rate,
return(amount); //and return amount
}
}
/// <summary>
/// Adds a new exchange rate to the ExchangeRate dictionary(string, float) if the
/// specified currencyCross is not already present in ExchangeRate or edits an entry
/// in the ExchangeRate dictionary if the specified currencyCross already exists.
/// </summary>
/// <param name="currencyCross">An existing cross
/// of two currencies in the format AAABBB.</param>
/// <param name="rate">A positive decimal number for the exchange rate.</param>
public void SpecifyExchangeRate(string currencyCross, double rate)
{
#region SpecifyExchangeRate sanity
//throw exception if currencyCross is empty,
//whitespace, or otherwise not 6 characters
//TODO: move to ExchangeRates property
if (String.IsNullOrWhiteSpace(currencyCross) || currencyCross.Length != 6)
{
throw new ArgumentException("Currency cross must be exactly six characters.");
}
//throw exception if currencyCross does not match an entry in CurrencyCrosses
if (!CurrencyCrosses.Contains(currencyCross))
{
throw new ArgumentException("Given currency cross does not exist.");
}
//throw exception if rate is not positive
if (rate <= 0)
{
throw new ArgumentException("Exchange rate must be positive");
}
#endregion
//check if currency cross already exist as an exchange rate
//if it does, edit existing exchange rate
//it it doesn't, add as new exchange rate(currencyCross, rate)
string reverseRate = currencyCross.Substring(3) + currencyCross.Substring(0, 3);
if (ExchangeRates.ContainsKey(currencyCross))
{
ExchangeRates[currencyCross] = rate;
}
else if (ExchangeRates.ContainsKey(reverseRate))
{
ExchangeRates[currencyCross] = 1 / rate;
}
else
{
ExchangeRates.Add(currencyCross, rate);
}
//go through ExchangeRates
//if any entry has a cross matching one of our currencyCross but not the other,
//also add an ExchangeRates entry for these two
bool crossFound = false;
string newCross = "";
foreach (string cross in ExchangeRates.Keys)
{
if (cross.Substring(0, 3) == currencyCross.Substring(0, 3)) //AAAbbb, AAAccc
{
newCross = cross.Substring(3) + currencyCross.Substring(3); //aaaBBB, aaaCCC
crossFound = true; //BBBCCC
}
else if (cross.Substring(0, 3) == currencyCross.Substring(3)) //AAAbbb, cccAAA
{
newCross = cross.Substring(3) + currencyCross.Substring(0, 3); //aaaBBB, CCCaaa
crossFound = true; //BBBCCC
}
else if (cross.Substring(3) == currencyCross.Substring(0, 3)) //bbbAAA, AAAccc
{
newCross = cross.Substring(0, 3) + currencyCross.Substring(3); //BBBaaa, aaaCCC
crossFound = true; //BBBCCC
}
else if (cross.Substring(3) == currencyCross.Substring(3)) //bbbAAA, cccAAA
{
newCross = cross.Substring(0, 3) + currencyCross.Substring(0, 3); //BBBaaa, CCCaaa
crossFound = true; //BBBCCC
}
string reverseRate2 = "";
if (!String.IsNullOrEmpty(newCross))
{
reverseRate2 = newCross.Substring(3) + newCross.Substring(0, 3);
}
if (crossFound && !ExchangeRates.ContainsKey(newCross) && ExchangeRates.ContainsKey(reverseRate2))
{
ExchangeRates.Add(newCross, ExchangeRates[cross] / rate);
crossFound = false;
}
}
}
