When should I define a (explicit or implicit) conversion operator in C#? [closed]

Answer 1

I use it to have seamless conversion from DateTime to "yyyyMMdd" or to its corresponding int (yyyyMMdd) value.

For example:

void f1(int yyyyMMdd);
void f2(string yyyyMMdd);

...
f1(30.YearsFrom(DateTime.Today));
f2(30.YearsFrom(DateTime.Today));

...
public static DateAsYyyyMmDd YearsFrom(this int y, DateTime d) 
{
    return new DateAsYyyyMmDd(d.AddYears(y));
}

...
public class DateAsYyyyMmDd
{
    private readonly DateTime date;

    public DateAsYyyyMmDd(DateTime date)
    {
        this.date = date;
    }

    public static implicit operator int(DateOrYyyyMmDd d)
    {
        return Convert.ToInt32(d.date.ToString("yyyyMMdd"));
    }

    public static implicit operator string(DateOrYyyyMmDd d)
    {
        return d.date.ToString("yyyyMMdd");
    }
}