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Constants (Delphi and C# Cross Reference Guide)

By Mike Prestwood

Delphi versus C#: A side by side comparison between Delphi and C#.

Language Basics

Language basics is kind of a catch all for absolute beginner stuff. The items (common names) I chose for language basics is a bit random and include items like case sensitivity, commenting, declaring variables, etc.


[Other Languages] 

General Info: Computer Language Constants

A constant is just like a variable (it holds a value) but, unlike a variable, you cannot change the value of a constant.

Delphi:   Const kPI: Double=3.1459;

In Delphi, you define constants similar to how you define variables but use the Const keyword instead of the Var keyword. Declare global constants in a unit's interface section and unit constants (scope limited to unit) in the implementation section. Declare local constants above the begin..end block.

Syntax Example:
  kFeetToMeter: Double = 3.2808;
  kMeterToFeet: Double = .3048;
  kName: String = "Mike";
//Local constants:
procedure SomeProcedure;
  kPI: Double=3.1459;
C#:   const

In C#, you define constants with the const keyword.

All constants are part of a class (no global constants) but you can make a constant public and have access to it using ClassName.ConstantName so long as you have added the class to the project. This works even without creating the class as if the public constants were static, but you cannot use the static keyword.

Constants must be of an integral type (sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, bool, or string), an enumeration, or a reference to null.

Syntax Example:  
public class Convert : Object
  public const string kName = "Mike";
  //You can declare multiple of the same type too:
  const Double kFeetToMeter = 3.2808, kMeterToFeet = .3048;

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