Question

I’m pretty sure this is a basic question but for some reason i can’t find it on Google as quick as I’d like so I’ll ask it here.

I’ve got a MoneyType object, which holds an int (value in cents) and a decimal (just the normal value)

This type inherits the IComperable interface and can be compared, now i’m comparing two MoneyTypes in an If statement:

if (invoice.GrossAmount == invoice.NetAmount)
{
 //Something
}

Now for what method should i override or what interface should i inherit to get this to work? Since doing this does not enter the CompareTo() method, neither does it enter the .Equals method so I’m at a loss atm.

Answer 1

If you implement IComparable, than you implement the CompareTo method. Based on this implementation, testing two amounts for equality is performed as:

if (invoice.GrossAmount.CompareTo(invoice.NetAmount) == 0)//the $ame amount of money
{..}

Comparing directly with “==” means overloading the “==” operator as described here. That is add the following method inside the MoneyType class:

public static bool operator ==(MoneyType x, MoneyType y) 
{
      return x.CompareTo(y.NetAmount) == 0;//make use of the working IComparable implementation
}

You must implement “!=”, too. You should also implement the Equals method (simply call the == operator) and the GetHashCode.

HTH,
Lucian