Using Conversion Operators (C# Programming Guide)
You can use implicit conversion operators, which are easier to use, or explicit conversion operators, which clearly indicate to anyone reading the code that you're converting a type. This topic demonstrates both types of conversion operator.
Note
For information about simple type conversions, see How to: Convert a String to a Number (C# Programming Guide), How to: Convert a byte Array to an int (C# Programming Guide), How to: Convert Between Hexadecimal Strings and Numeric Types (C# Programming Guide), or Convert.
Example
This is an example of an explicit conversion operator. This operator converts from the type Byte to a value type called Digit. Because not all bytes can be converted to a digit, the conversion is explicit, meaning that a cast must be used, as shown in the Main method.
struct Digit
{
byte value;
public Digit(byte value) //constructor
{
if (value > 9)
{
throw new System.ArgumentException();
}
this.value = value;
}
public static explicit operator Digit(byte b) // explicit byte to digit conversion operator
{
Digit d = new Digit(b); // explicit conversion
System.Console.WriteLine("Conversion occurred.");
return d;
}
}
class TestExplicitConversion
{
static void Main()
{
try
{
byte b = 3;
Digit d = (Digit)b; // explicit conversion
}
catch (System.Exception e)
{
System.Console.WriteLine("{0} Exception caught.", e);
}
}
}
// Output: Conversion occurred.
This example demonstrates an implicit conversion operator by defining a conversion operator that undoes what the previous example did: it converts from a value class called Digit to the integral Byte type. Because any digit can be converted to a Byte, there's no need to force users to be explicit about the conversion.
struct Digit
{
byte value;
public Digit(byte value) //constructor
{
if (value > 9)
{
throw new System.ArgumentException();
}
this.value = value;
}
public static implicit operator byte(Digit d) // implicit digit to byte conversion operator
{
System.Console.WriteLine("conversion occurred");
return d.value; // implicit conversion
}
}
class TestImplicitConversion
{
static void Main()
{
Digit d = new Digit(3);
byte b = d; // implicit conversion -- no cast needed
}
}
// Output: Conversion occurred.
See Also
Reference
Conversion Operators (C# Programming Guide)