下面是一些按原样编译并完成这项工作的代码。
基本上使用两个字典，一个包含从操作符名称到布尔函数的映射，另一个包含从User类型的属性名称到用于调用属性getter(如果是公共的)的PropertyInfos的映射。
将User实例和表中的三个值传递给静态Apply方法。
class User
{
public int Age { get; set; }
public string UserName { get; set; }
}
class Operator
{
private static Dictionary<string, Func<object, object, bool>> s_operators;
private static Dictionary<string, PropertyInfo> s_properties;
static Operator()
{
s_operators = new Dictionary<string, Func<object, object, bool>>();
s_operators["greater_than"] = new Func<object, object, bool>(s_opGreaterThan);
s_operators["equal"] = new Func<object, object, bool>(s_opEqual);
s_properties = typeof(User).GetProperties().ToDictionary(propInfo => propInfo.Name);
}
public static bool Apply(User user, string op, string prop, object target)
{
return s_operators[op](GetPropValue(user, prop), target);
}
private static object GetPropValue(User user, string prop)
{
PropertyInfo propInfo = s_properties[prop];
return propInfo.GetGetMethod(false).Invoke(user, null);
}
#region Operators
static bool s_opGreaterThan(object o1, object o2)
{
if (o1 == null || o2 == null || o1.GetType() != o2.GetType() || !(o1 is IComparable))
return false;
return (o1 as IComparable).CompareTo(o2) > 0;
}
static bool s_opEqual(object o1, object o2)
{
return o1 == o2;
}
//etc.
#endregion
public static void Main(string[] args)
{
User user = new User() { Age = 16, UserName = "John" };
Console.WriteLine(Operator.Apply(user, "greater_than", "Age", 15));
Console.WriteLine(Operator.Apply(user, "greater_than", "Age", 17));
Console.WriteLine(Operator.Apply(user, "equal", "UserName", "John"));
Console.WriteLine(Operator.Apply(user, "equal", "UserName", "Bob"));
}
}
