We learned about arrays in C# in a
, so let’s spend a moment comparing them to
Lists are generally easier to use than C#’s
Array. Let’s see why this is.
Why does C# have both
Lists? The answer is historical, at least in part. C# is a C-style language, and arrays are the most basic data structure in C.
Array over a
List might be preferred in some circumstances, primarily for performance reasons (array operations are generally faster than
List operations). Also note that
Arrays are of fixed size. You cannot expand or contract an
Array after it is created, so you must know exactly how many elements it will need to hold when you create it. This fact is reason enough to use
Lists in most scenarios.
Array usage, here is a version of the
Gradebook program using
Arrays instead of
ArrayGradebook project is in
ArrayGradebook project lives in the
csharp-web-dev-controlflowandcollections repository. If you haven’t forked and cloned the repository, you should do so now.
Note that we have to decide up front how large our arrays,
grades, are going to be. Thus, this program sets an arbitrary maximum amount of students, likely larger than any user will enter. It may seem obvious, then, that
Array has no equivalent
Add() method. The only way to access and alter an element in an
Array is with bracket notation, using an explicit index. For example, gradebook defines a counter variable,
numStudents. When the first student is entered by the user, the value is stored in newStudent. If the value is not the empty string, then the value in students at position 0 is assigned the
newStudent value. The next time the
do-while loop executes, the value of
students at position 1 will be assigned. This process continues until the user enters an empty string for
newStudent. Because we must always access and assign
Array elements using an explicit index, our code can seem littered with
Array counter variables (like our friends
j), making it more difficult to read (not to mention more error-prone).
Lists, however, we can loop through an
Array using a
foreach loop as long as we don’t need to use the index of the current item. If we only wanted to print each student’s name, and not their grade, at the end of our program, we could do the following:
Arrays in C# from time-to-time, but for the most part you should rely on
Lists to store collections of values, or ordered data.
Array size and element values cannot be changed once defined.
Array below, which of the following options is a valid action?
int randomNumbers = new int;
randomNumbers = "three";
randomNumbers = 1;