explicit keyword (C# Conversion Keywords)

The explicit keyword declares a user-defined type conversion operator that must be invoked with a cast. The conversion operator converts from a source type to a target type. The source type provides the conversion operator. Unlike implicit conversion, explicit conversion operators must be invoked by means of a cast.

Omitting the cast results in compile-time error CS0266.

Example: The following example provides a Fahrenheit and a Celsius class, each of which provides an explicit conversion operator to the other class.

class Celsius

{

public Celsius(float fTemp)

{

fDegrees = fTemp;

}

// Must be defined inside a class called Celsius:

public static explicit operator Fahrenheit(Celsius c)

{

return new Fahrenheit((9.0f / 5.0f) * c.fDegrees + 32);

}

public float Degrees

{

get { return fDegrees; }

}

private float fDegrees;

}

class Fahrenheit

{

public Fahrenheit(float fTemp)

{

fDegrees = fTemp;

}

// Must be defined inside a class called Fahrenheit:

public static explicit operator Celsius(Fahrenheit fahr)

{

return new Celsius((5.0f / 9.0f) * (fahr.fDegrees - 32));

}

public float Degrees

{

get { return fDegrees; }

}

private float fDegrees;

}

class MainClass

{

static void Main()

{

Fahrenheit oFahrenheit = new Fahrenheit(100.0f);

Console.Write("{0} Fahrenheit", oFahrenheit.Degrees);

Celsius oCelsius = (Celsius)oFahrenheit; // Calls explicit conversion operator in Fahrenheit class

Console.Write(" = {0} Celsius", oCelsius.Degrees);

Fahrenheit oFahrenheit2 = (Fahrenheit)oCelsius; // Calls explicit conversion operator in Celsius class

Console.WriteLine(" = {0} Fahrenheit", oFahrenheit2.Degrees);

}

}