c# - 动态评估属性的通用函数

Question

我有以下类(class):

public class Vehicle
{
    public string Name { get; set; }
    public bool CanFly { get; set; }
    public bool CanDive { get; set; }
}

public class Hdd
{
    public string Name { get; set; }
    public bool CanRead { get; set; }
    public bool CanWrite { get; set; }
    public bool CanCopy { get; set; }
}

我想编写一个函数来过滤例如是否存在特定汽车(按 firstOrDefault 名称过滤)然后检查给定条件作为参数，例如 CanFly 或 CanDive ...等

所以我在想:

public class TestProperties
{
    public bool Check<T>(List<T> items, string name,
        Expression<Func<T, bool>> expression)
    {
        var expr = (MemberExpression)expression.Body;
        var prop = (PropertyInfo)expression.Member;
        //1- Filter items with the given name
        // return false if no records found
        // return false if the condition fails 
    }
}

然后我会调用函数如下

var myHdds= GetHdd();
var myCars= GetCars();
var CanRead = Check<Hdd>(myHdds,"samsung",x => x.CanRead);
var CanFly = Check<Vehicle>(myCars,"Audi",x => x.CanFly);

如何实现检查功能？

Answer 1

你快到了。尝试这个 -

public bool Check<T>(List<T> items, Expression<Func<T, bool>> expression)
{
    return items.Any(x => expression.Compile()(x));
} 

或者，

public bool Check<T>(List<T> items, Func<T, bool> compiledExp)
{
    return items.Any(x => compiledExp(x));
} 

并像这样打电话 -

Check<Vehicle>(myCars, x => x.Name == "Audi" && x.CanFly);
Check<Hdd>(myHdds,x => x.Name == "Samsung" &&  x.CanRead);

但现在想想，你真的不需要一种方法来做到这一点。它实际上是一行代码。

我个人更喜欢扩展方法 -

public static bool Check<T>(this List<T> items, Func<T, bool> compiledExp)
{
    return items.Any(x => compiledExp(x));
} 

并调用 -

myHdds.Check(x => x.Name == "Samsung" &&  x.CanRead);