How to implement a rule engine?

I have a db table that stores the following:

RuleID  objectProperty ComparisonOperator  TargetValue
1       age            'greater_than'             15
2       username       'equal'             'some_name'
3       tags           'hasAtLeastOne'     'some_tag some_tag2'

Now say I have a collection of these rules:

List<Rule> rules = db.GetRules();

Now I have an instance of a user also:

User user = db.GetUser(....);

How would I loop through these rules, and apply the logic and perform the comparisons etc?

if(user.age > 15)

if(user.username == "some_name")

Since the object’s property like ‘age’ or ‘user_name’ is stored in the table, along with the comparison operater ‘great_than’ and ‘equal’, how could I possible do this?

C# is a statically typed language, so not sure how to go forward.