var exp1 = @event.ToDto<CustomerCreatedEvent,CustomerDetail>( x=> x.AggregateId.As("CustomerId"), x => x.Email, x => x.FirstName, x => x.Surname);

TestExtensions.cs

          public static dynamic ToDynamic(this object value)
            {
                IDictionary<string, object> expando = new ExpandoObject();

                foreach (PropertyDescriptor property in TypeDescriptor.GetProperties(value.GetType()))
                    expando.Add(property.Name, property.GetValue(value));

                return expando as ExpandoObject;
            }

            public static KeyValuePair<string, object> As(this object obj, string rename)
            {
                return new KeyValuePair<string, object>(rename, obj);
            }
       
       
       public static T2 ToDto<T1,T2>(this T1 obj, params Expression<Func<T1, dynamic>>[] items) where T1 : class
            {
                var eo = new ExpandoObject();
                var props = eo as IDictionary<String, object>;

                foreach (var thing in items)
                {
                    var member = thing.Body as MemberExpression;
                    var unary = thing.Body as UnaryExpression;
                    var body = member ?? (unary != null ? unary.Operand as MemberExpression : null);

                    if (member != null && body.Member is PropertyInfo)
                    {
                        var property = body.Member as PropertyInfo;
                        if (property != null)
                            props[property.Name] = obj.GetType().GetProperty(property.Name).GetValue(obj, null);
                    }
                    else if (unary != null)
                    {
                        var ubody = (UnaryExpression)thing.Body;
                        var property = ubody.Operand as MemberExpression;
                        if (property != null)
                        {
                            props[property.Member.Name] = obj.GetType()
                                .GetProperty(property.Member.Name)
                                .GetValue(obj, null);
                        }
                        else // full expression with number funcs
                        {
                            var compiled = thing.Compile();
                            var result = (KeyValuePair<string, object>)compiled.Invoke(obj);
                            props[result.Key] = result.Value;
                        }
                    }
                }

                string json = JsonConvert.SerializeObject(eo);  // need json.net
                var anon = JsonConvert.DeserializeAnonymousType<object>(json, Activator.CreateInstance<T2>());
                return ((JObject)anon).ToObject<T2>();
            }