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Note

The C# 

ref

keyword will be revisited later in this chapter in the section “Understanding Value Types and

Reference Types.” As you will see, the behavior of this keyword changes just a bit depending on whether the argu-

ment is a “value type” (structure) or “reference type” (class).

The params Modifier

Last but not least, C# supports the use of parameter arrays. To understand the role of the params

keyword, you must (as the name implies) understand how to manipulate C# arrays. If this is not the

case, you may wish to return to this section once you have finished this chapter, as we will formally

examine the System.Array type a bit later in this chapter in the section “Array Manipulation in C#.”

The params keyword allows you to pass into a method a variable number of parameters (of the

same type) as a 

single logical parameter. As well, arguments marked with the params keyword can be

processed if the caller sends in a strongly typed array or a comma-delimited list of items. Yes, this

can be confusing! To clear things up, assume you wish to create a function that allows the caller to

pass in any number of arguments and return the calculated average.

If you were to prototype this method to take an array of doubles, this would force the caller to

first define the array, then fill the array, and finally pass it into the method. However, if you define

CalculateAverage() to take a params of integer data types, the caller can simply pass a comma-

delimited list of doubles. The .NET runtime will automatically package the set of doubles into an

array of type double behind the scenes: