transform string to decimal

Question

This feels wrong:

private decimal ConvertStringToDecimal(string decimalString, decimal defaultReturnValue)
{
 var returnDecimal = defaultReturnValue;
 try
 {
 returnDecimal = decimal.Parse(decimalString.Trim());
 }
 catch (Exception)
 {
 // naughty
 }
 return returnDecimal;
}

but I think this is the only way to transform a string from a third party system to a decimal whilst returning a default. Does anyone have any suggestions on how to improve this?

Answer 1

The easiest and most clean way would be to use decimal.TryParse() like so

private decimal ConvertStringToDecimal(string decimalString, decimal defaultReturnValue)
{
 decimal result;
 if (decimal.TryParse(decimalString.Trim(), out result))
 {
 return result;
 }
 return defaultReturnValue;
} 

Using exceptions to control the returned value isn't a good way, especially if there are better methods to use.

Your indentation is off but I assume that thats a posting issue.

• cs0815: oh yeah - forgot about that method (-:
• Morgen: I really don't understand why they did it this way, Java also uses exceptions for flow control when converting to numeric values. It's comforting that c# has a better alternative. Hopefully Java will "borrow" this method in the next version :)
• Caridorc: @Morgen I have mixed feelings about the out parameter, it feels so low level...
• Morgen: @Caridorc I agree, still much better than throwing an exception as you don't incur the cost of building a stack trace every time the user gives you a malformed number. Returning a Maybe/Option type would be even better.

Answer 2

You can write the equivalent shorter, using the ternary operator ?: and decimal.tryParse, like this:

private decimal ConvertStringToDecimal(string decimalString, decimal defaultReturnValue)
{
 decimal value = decimal.TryParse(decimalString, out value) ? value : defaultReturnValue;
 return value;
}