C# Programming/Keywords/implicit



When values are cast implicitally, the runtime does not need any casting in code by the developer in order for the value to be converted to its new type.

Here is an example, where the developer is casting explicitly:

// Example of explicit casting.
float fNumber = 100.00f;
int iNumber = (int) fNumber;

The developer has told the runtime, "I know what I'm doing, force this conversion."

Implicit casting means that runtime doesn't need any prompting in order to do the conversion. Here is an example of this.

// Example of implicit casting.
byte bNumber = 10;
int iNumber = bNumber;

Notice that no casting was necessary by the developer. What is special about implicit is that the context that the type is converted to is totally lossless, i.e. converting to this type loses no information. So, it can be converted back without worry.



The keyword implicit is used for a type to define how to can be converted implicitly. It is used to define what types can be converted to without the need for explicit casting.

As an example, let us take a Fraction class, that will hold a nominator (the number at the top of the division), and a denominator (the number at the bottom of the division). We will add a property so that the value can be converted to a float.

public class Fraction
     private int nominator;
     private int denominator;

     public Fraction(int nominator1, int denominator1)
          nominator = nominator1;
          denominator = denominator1;

     public float Value { get { return (float)_nominator/(float)_denominator; } }

     public static implicit operator float(Fraction f)
          return f.Value;

     public override string ToString()
          return _nominator + "/" + _denominator;

public class Program
     public static void Main(string[] args)
          Fraction fractionClass = new Fraction(1, 2);
          float number = fractionClass;

          Console.WriteLine("{0} = {1}", fractionClass, number);

To re-iterate, the value it implicitally casts to must hold data in the form that the original class can be converted back to. If this is not possible, and the range is narrowed (like converting double to int), use the explicit operator.

C# Keywords
abstract as base bool break
byte case catch char checked
class const continue decimal default
delegate do double else enum
event explicit extern false finally
fixed float for foreach goto
if implicit in int interface
internal is lock long namespace
new null object operator out
override params private protected public
readonly ref return sbyte sealed
short sizeof stackalloc static string
struct switch this throw true
try typeof uint ulong unchecked
unsafe ushort using var virtual
void volatile while
Special C# Identifiers (Contextual Keywords)
add alias async await dynamic
get global nameof partial remove
set value when where yield
Contextual Keywords (Used in Queries)
ascending by descending equals from
group in into join let
on orderby select where