Thus far, we’ve been able to start building some pretty cool applications. There’s one big missing piece though when it comes to storing data: What happens when we need to store many things of the same kind? For example, what if you’re building an application that allows a user to create a music playlist. How many variables will you need? One string variable per song? What if you need to store a couple songs, one hundred songs, or even one thousand songs!? This could become a massive headache if we stored one song per variable. Luckily, there’s a solution to this problem.
Programming languages have a way to store many things together in a group. These are known as data structures. C# provides a data type known as an array that is capable of storing data of the same type in a collection. An important feature of an array is that it is of a fixed size, meaning that the number of items an array can store must be determined when it is initialized.
string[] friends;
The variable titled friends is capable of storing a collection of strings.
string[] friends = new string[100];
The friends array has now been initialized and is capable of storing 100 strings. Values of an array are referred to as elements. The array is only ever capable of storing 100 elements. This is a limitation of arrays in that they are not resizable. There are other data structures available when you need a collection type that can resize as needed.
Elements in an array are positioned in sequence. Their positions are referred to as indexes. Arrays begin indexing elements at position 0. Therefore, the friends array can index elements of the range between 0 and 99.
// Assign element at index 0, or the first index
friends[0] = "Mortimer";
friends[1] = "Schilf";
friends[2] = "Rupanovic";
Notice the square bracket notation is a common indicator that we’re working with arrays.
// Access elements of the friends array
Console.WriteLine($"I am friends with {friends[0]}, {friends[1]}, and {friends[2]}.");
If you attempt to access an element outside of the available indexes, such as friends[500], your program will crash and you will receive an IndexOutOfRangeException. You may not attempt to access elements outside of the specified range.
If the values to be inserted into the array are pre-determined, you may use array initialization syntax to pre-populate an array. Note that the number of elements you assign at initialization will determine the array’s size.
// Initialize an array with three elements. This array has a capacity of 3 elements.
double [] accounts = new double[]{ 1000.50, 999.99, 2530.02 };
string[] besties = new string[3]; // 3 empty elements
besties[0] = "Mr. Fistek";
besties[1] = "Mr. Barrett";
Console.Write("Which teacher is your bestie? ");
besties[2] = Console.ReadLine();
Console.WriteLine($"My besties are {besties[0]}, {besties[1]}, and {besties[2]}!\n");
Console.WriteLine("Press enter to continue...");
Console.ReadLine();
Console.WriteLine("--- Gradebook ---");
// Initialize array with 5 elements.
double[] grades = new double[]{ 90, 88, 95, 60, 85 };
double totalPoints = grades[0] + grades[1] + grades[2] + grades[3] + grades[4];
// Assuming grades are out of 100. Total possible points = 500
// Multiply by 100 to get percentage as a whole number
double gradePercentage = Math.Round(totalPoints / 500 * 100);
string letterGrade;
if (gradePercentage > 90)
{
letterGrade = "A";
}
else if (gradePercentage > 80)
{
letterGrade = "B";
}
else if (gradePercentage > 70)
{
letterGrade = "C";
}
else if (gradePercentage > 60)
{
letterGrade = "D";
}
else
{
letterGrade = "F";
}
Console.WriteLine($"Grades: {grades[0]}, {grades[1]}, {grades[2]}, {grades[3]}, {grades[4]}");
Console.WriteLine($"Final grade: {gradePercentage}%. Letter grade: {letterGrade}");
Which teacher is your bestie? Mr. Mortimer
My besties are Mr. Fistek, Mr. Barrett, and Mr. Mortimer!
Press enter to continue...
--- Gradebook ---
Grades: 90, 88, 95, 60, 85
Final grade: 84%. Letter grade: B