C# Language Casting Conversion Operators
Example
In C#, types can define custom Conversion Operators, which allow values to be converted to and from other types using either explicit or implicit casts. For example, consider a class that is meant to represent a JavaScript expression:
public class JsExpression
{
private readonly string expression;
public JsExpression(string rawExpression)
{
this.expression = rawExpression;
}
public override string ToString()
{
return this.expression;
}
public JsExpression IsEqualTo(JsExpression other)
{
return new JsExpression("(" + this + " == " + other + ")");
}
}
If we wanted to create a JsExpression representing a comparison of two JavaScript values, we could do something like this:
JsExpression intExpression = new JsExpression("-1");
JsExpression doubleExpression = new JsExpression("-1.0");
Console.WriteLine(intExpression.IsEqualTo(doubleExpression)); // (-1 == -1.0)
But we can add some explicit conversion operators to JsExpression, to allow a simple conversion when using explicit casting.
public static explicit operator JsExpression(int value)
{
return new JsExpression(value.ToString());
}
public static explicit operator JsExpression(double value)
{
return new JsExpression(value.ToString());
}
// Usage:
JsExpression intExpression = (JsExpression)(-1);
JsExpression doubleExpression = (JsExpression)(-1.0);
Console.WriteLine(intExpression.IsEqualTo(doubleExpression)); // (-1 == -1.0)
Or, we could change these operators to implicit to make the syntax much simpler.
public static implicit operator JsExpression(int value)
{
return new JsExpression(value.ToString());
}
public static implicit operator JsExpression(double value)
{
return new JsExpression(value.ToString());
}
// Usage:
JsExpression intExpression = -1;
Console.WriteLine(intExpression.IsEqualTo(-1.0)); // (-1 == -1.0)
