TryParse_improved1.cs

public static bool TryParse(object number, out int result)
{
    switch (number)
    {
        case int i:
            result = i;
            return true;
        case string s:
            return ParseString(s, out result);
        default:
            throw new NotSupportedException($"{nameof(IntegerParser)} only accepts strings ans integers, type '{number.GetType()}' is not supported");
    }
}