Question

I’m sure this is a stupid question, but why does the following code not call the explicit operator for the cast on the child class MyBool?

public class DataType
{
    public static explicit operator bool(DataType D)
    {
        return false;
    }

    public static explicit operator DataType(bool B)
    {
        return new DataType();
    }
}

public class MyBool : DataType
{
    public bool Value;

    public MyBool()
    {
        Value = false;
    }

    public static explicit operator bool(MyBool B)
    {
        return B.Value;
    }

    public static explicit operator MyBool(bool B)
    {
        return new MyBool() { Value = B };
    }
}

then:

List<DataType> Types = new List<DataType>();

Types.Add(new MyBool() { Value = true });
Types.Add(new MyBool() { Value = false });

foreach (DataType T in Types)
{
    bool Value = (bool)T;
    MessageBox.Show(Value.ToString());
}

Produces the output: false, false

Is my only option to write functions on each class to take the place of the explicit operator functions?

Answer 1

why does the following code not call the explicit operator for the cast on the child class MyBool?

Because the operator functions are static, hence also non-virtual and thus their target is resolved at compile time rather than runtime. This is the expected behaviour.

If you want to have polymorphic conversion operators you can call virtual functions inside the operators:

public abstract class DataType
{
    public static explicit operator bool(DataType D)
    {
        return D.DoCastToBool();
    }

    public static explicit operator DataType(bool B)
    {
        // We haven’t got an instance of our class here.
        // You can use a factory method pattern to emulate virtual constructors.
    }

    protected abstract bool DoCastToBool();
}