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// The iteration of the Car can be ordered

// based on the CarID.

public class Car : IComparable

{

...

// IComparable implementation.

int IComparable.CompareTo(object obj)

{

Car temp = (Car)obj;

if(this.carID > temp.carID)

return 1;

if(this.carID < temp.carID)

return -1;

else

return 0;

}

}

As you can see, the logic behind CompareTo() is to test the incoming type against the current

instance based on a specific point of data. The return value of CompareTo() is used to discover

whether this type is less than, greater than, or equal to the object it is being compared with (see

Table 9-1).

Table 9-1. CompareTo() Return Values

CompareTo() Return Value

Meaning in Life

Any number less than zero

This instance comes before the specified object in the sort

order.

Zero

This instance is equal to the specified object.

Any number greater than zero

This instance comes after the specified object in the sort order.

We can streamline the previous implementation of CompareTo() given the fact that the C# int

data type (which is just a shorthand notation for the CLR System.Int32) implements IComparable;

you could implement the Car’s CompareTo() as follows:

int IComparable.CompareTo(object obj)

{

Car temp = (Car)obj;

return this.carID.CompareTo(temp.carID);

}

In either case, so that your Car type understands how to compare itself to like objects, you can

write the following user code: