type Class5<'T when 'T : (member Method1 : 'T * string * decimal -> int)>(dataIn) =
    let data = dataIn

where T : new(int, string, DataTime)

   public abstract class Expression
    {
        public sealed class Number : Expression
        {
            public Number(int value)
            {
                Value = value;
            }
            public int Value { get; private set; }
        }
        public sealed class Add : Expression
        {
            public Add(Expression left, Expression rigth)
            {
                Left = left;
                Rigth = rigth;
            }
            public Expression Left { get; private set; }
            public Expression Rigth { get;private set; }
        }
        public sealed class Multiply : Expression
        {
            public Multiply(Expression left, Expression rigth)
            {
                Left = left;
                Rigth = rigth;
            }
            public Expression Left { get;private set; }
            public Expression Rigth { get;private set; }
        }
        public sealed class Variable:Expression
        {
            public Variable(string str)
            {
                Value = str;
            }
            public string Value { get; private set; }
        }
        public static int Evaluate(Dictionary<string, int> env, Expression expression)
        {
            switch(expression)
            {
                case Number n:
                    return n.Value;
                case Add add:
                    return Evaluate(env, add.Left) + Evaluate(env, add.Rigth);
                case Multiply mul:
                    return Evaluate(env, mul.Left) + Evaluate(env, mul.Rigth);
                case Variable variable:
                    return env[variable.Value];
                default:
                    throw new Exception();
            }
        }
    }