[C#] C# Named Constants

📋 This is my note-taking from what I learned in the class “Programming 1 - COMP 100-002”

What are Named Constants?

• Are immutable.

  Values that would not change in the life of the program.

• Must be known at compile time (must be set at declaration).

  Has to be a literal or a constant expression.

• Only C# built-in types may be declared constant (except objects).

Usage

• Value is set at declaration.

• In your code, it is used like a normal variable.

• It can not appear on the left side of an expression after declaration.

  → You may not assign a new value to it.

Example:

const string COMPANY_NAME = "Centennial College";
const char SPACE = ' ';
const double TAX_RATE = 0.13;
const int LEGAL_AGE = 18;
const int MONTHS = 12, DAYS = 365;
const double DAYS_PER_MONTH = DAYS / (double)MONTHS;

cost = price * (1 + TAX_RATE);

Why Use Named Constants?

• Improves readability of your code.

  You see words not values.

• Code maintenance.

  Easier to edit code.

  If you have the same literal value for two items and you want to change one of them, it is almost impossible to make a certain change.

• Security.

  Value may not change during execution of program.

“ToUpper” and “ToLower” Methods

• These string methods returns a string that is all uppercased or all lowercased.
• They only work with strings (Does not work with char).
• It is convenient when doing string comparisons.
• If a user is asked to the two letter province code.

• For this province the user response might be any of the following:

  → ON, On, on, oN

• To simplify processing the response, you can decide to compare either the uppercased or the lowercased version the response.

Example:

Console.Write("What shape would you like to work with? ");

string shape = Console.ReadLine();

switch(shape.ToLower())
{
  case "square":
    Console.WriteLine($"The area of a {shape} is length x width");
    break;
  case "triangle":
    Console.WriteLine($"The area of a {shape} is base x height / 2");
    break;
}

Console.WriteLine($"{shape} -> {shape.ToUpper()}"); // shape does not change

• Named constants is having a name for a value that may not change.
• You have the confidence that it will not change in the execution of the application.
• Your code is more readable.
  • You see a descriptive name instead of a literal value.
• Code maintenance is simpler.

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