在表达式中引用通用属性

发布于 2024-07-24 03:05:58 字数 605 浏览 1 评论 0原文

假设我有两张桌子，午餐和晚餐。我知道两者都包含日期时间属性“时间”。

如果我有一个通用方法 GetTime，当 T 是午餐时我如何返回 db.Lunch.Time，当 T 是晚餐时如何返回 db.Dinner.Time？我试图在不使用 typeof 单独测试 T 的情况下实现这一目标，而是一般性地测试。

伪代码：

public T GetTime<T>(DateTime dt)
{
    return MyDataContext.GetTable<T>().Where(entity => entity.Time == dt);
}

所以当我调用 GetTime时它将自动在餐桌上查找属性时间等于我提供的参数 dt 的所有晚餐实体。

问题是我无法在表达式中指定 entity.Time 因为 T 是泛型。我的问题是如何解决这个问题，以便我可以查找任何 T（知道我的所有实体实际上都有 Time 属性），而无需为晚餐和午餐创建特定方法。

原文

Let's say I have two Tables, Lunch and Dinner. I know that both contain the DateTime property "Time".

If I have a generic method GetTime, how could I return db.Lunch.Time when T is Lunch and db.Dinner.Time when T is Dinner? I'm trying to achieve this without testing for T individually using typeof, but rather generically.

Pseudocode:

public T GetTime<T>(DateTime dt)
{
    return MyDataContext.GetTable<T>().Where(entity => entity.Time == dt);
}

So when I call GetTime<Dinner> it will automatically look in the Dinner Table for all dinner entities with the property time equal to my supplied parameter dt.

The problem is that I can't specifiy entity.Time in my expression because T is a generic. My question is how to get around that, so that I can look for any T (knowing that all my entities in fact have the Time property) without having to create specific methods for Dinner and Lunch.

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氛圍 2024-07-31 03:05:58

你必须让两个类都实现一个类似这样的接口：

public interface IMyInterface
{
   DateTime Time{get;set;}
}

然后在你的通用方法中：

public void MyMethod<T>(T item) where T: IMyInterface
{
    //here you can access item.Time
}

You'd have to have both classes implement an interface something like this:

public interface IMyInterface
{
   DateTime Time{get;set;}
}

And then in your generic method:

public void MyMethod<T>(T item) where T: IMyInterface
{
    //here you can access item.Time
}

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命比纸薄 2024-07-31 03:05:58

您可以使用午餐和晚餐实现的接口，该接口具有名为 Time 的属性

 public interface IMealTime
    {
        DateTime Time { get; set; }
    }

    public class Lunch : IMealTime
    {
        #region IMealTime Members

        public DateTime Time { get; set; }

        #endregion
    }

    public class Dinner : IMealTime
    {
        #region IMealTime Members
        public DateTime Time { get; set; }

        #endregion
    }

    public class GenericMeal
    {
        public DateTime GetMealTime<T>(T meal) where T: IMealTime
        {
            return meal.Time;
        }
    }

You could use an interface that Lunch and Dinner implement that has a property called Time

 public interface IMealTime
    {
        DateTime Time { get; set; }
    }

    public class Lunch : IMealTime
    {
        #region IMealTime Members

        public DateTime Time { get; set; }

        #endregion
    }

    public class Dinner : IMealTime
    {
        #region IMealTime Members
        public DateTime Time { get; set; }

        #endregion
    }

    public class GenericMeal
    {
        public DateTime GetMealTime<T>(T meal) where T: IMealTime
        {
            return meal.Time;
        }
    }

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