c# - 取决于类型 T 的枚举

Question

我有一个通用类需要根据定义的类型限制枚举:

public enum ConditionOperatorsString { None, Like, Equal }
public enum ConditionOperatorsDate { None, Equal, BeforeThan, AfterThan }
public class Condition<T>
{
  public T Value { get; set; }
  public ConditionOperatorsString Operator { get; set; }
  public Condition(T Value, ConditionOperatorsString Operator)
  {
    this.Value = Value;
    this.Operator = Operator;
  }
}

现在的问题是我希望 Operator 类型依赖于 T 所以当:

Condition<string> CStr= new Condition<string>(string.Empty, ConditionOperatorsString.None)
Condition<DateTime> CStr= new Condition<DateTime>(DateTime.Now, ConditionOperatorsDate.None)

如何为此定义类条件？我想到了一个接口(interface)，但枚举不会从接口(interface)继承。

Answer 1

没有好的方法可以做你想做的事情，在你的构造函数中是这样的:

if (typeof(T) == typeof(string) && 
    typeof(Operator) != typeof(ConditionOperatorsString))
{ 
    throw new Exception("Invalid conditionoperators value);
}

这真的不是很有用，因为你必须提前知道 T 的所有不同可能性。

你可以做的事情是这样的:

public abstract class ComparableBase<T,K>
{
    public T Value { get; protected set; }
    public K ConditionOperator { get; protected set; }
    // public abstract bool IsMatch(T other); // Is this required?

    protected ComparableBase(T value, K op)
    {
        this.Value = value;
        this.ConditionOperator = op;
    }
}

public enum ComparableOperator { None, Equal, Less, Greater }

public enum LikeOrEqualOperator { None, Like, Equal }

public class ComparableCondition<T> : ComparableBase<T,ComparableOperator>
{
    public ComparableCondition(T value, ComparableOperator op):base(value, op)
    {
    }
}

public class LikeOrEqualCondition<T> : ComparableBase<T, LikeOrEqualOperator>
{
    public LikeOrEqualCondition(T value, LikeOrEqualOperator op):base(value, op)
    {
    }
}

然后你可以声明

var condition1 = new LikeOrEqualCondition<string>("hi", LikeOrEqualOperator.Equal);

你需要有一个IsMatch吗？或者这是为了显示选定的过滤器，而不是实际实现它。

如果你这样做，事情会稍微复杂一点......