C# 5.0 Programmer's Reference

632 ❘ APPENDIX A Solutions to Exercises
copy of x’s value. The pre-increment operator can work only on items such as variables that it
can increment, so it fails.
If you enter ++x++ in the code, Visual Studio flags it with this error:
The operand of an increment or decrement operator must be a variable, property or indexer
2. The following code uses if statements instead of : and .
if (amount < 0) amountLabel.ForeColor = Color.Red;
else amountLabel.ForeColor = Color.Blue;
Customer orderedBy;
if (customer != null) orderedBy = customer;
else orderedBy = new Customer();
The following code shows a slightly more concise way to set orderedBy.
Customer orderedBy = customer;
if (customer == null) orderedBy = new Customer();
3. The code starts by using System.Object.ReferenceEquals to see if the operands refer
to the same object. If they are both null, then they refer to the same null object, so the
method returns true.
4. The following code shows a subtraction operator for the Complex class.
public static Complex operator -(Complex operand1, Complex operand2)
{
return new Complex()
{
Re = operand1.Re - operand2.Re,
Im = operand1.Im - operand2.Im
};
}
Alternatively, because the class already defines addition and unary negation, you could use
the following simpler subtraction operator.
public static Complex operator -(Complex operand1, Complex operand2)
{
return operand1 + (-operand2);
}
5. The following code shows a simple Fraction class with * and / operators.
public class Fraction
{
public double Numerator = 0;
public double Denominator = 0;
public static Fraction operator *(Fraction operand1, Fraction operand2)
{
return new Fraction()
{
Numerator = operand1.Numerator * operand2.Numerator,
Denominator = operand1.Denominator * operand2.Denominator
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