custom cast c#
using System;
public readonly struct Digit
{
private readonly byte digit;
public Digit(byte digit)
{
if (digit > 9)
{
throw new ArgumentOutOfRangeException(nameof(digit), "Digit cannot be greater than nine.");
}
this.digit = digit;
}
public static implicit operator byte(Digit d) => d.digit;
public static explicit operator Digit(byte b) => new Digit(b);
public override string ToString() => $"{digit}";
}