使用 LINQ 过滤通用列表，使用 PropertyName 作为字符串文字 - 使用动态

Question

我想知道这种方法是否可以做得更好。我需要过滤作为字符串传入的成员名称上的通用列表。我的想法是将通用列表转换为动态列表，然后将 expandoObject 转换为 Dictionary 并检查成员名称是否存在。最后，使用 JsonSerializer 将动态列表转换回通用列表。您对更好的实施有何想法？反射？动态 LINQ（Scott Guthrie 在 2008 年做了一些工作）？表达式树？

        public static IEnumerable<T> FilterListByStringPropertyName<T>(this IEnumerable<T> genericList, int? enumId, string enumFieldName)
    {
        if (string.IsNullOrEmpty(enumFieldName))
        {
            throw new NullReferenceException("FilterByEnum: enumFieldName cannot be empty");
        }

        if (enumId == null)
        {
            //skip method as no filtering needed
            return genericList;
        }

        if (genericList.Count() == 0)
        {
            return genericList;
        }

        List<T> @return = new List<T>();
        List<dynamic> dynamicList = new List<dynamic>();

        //fill the dynamic list from generic list
        foreach (var genericItem in genericList)
            dynamicList.Add(genericItem.ToDynamic());

        var first = dynamicList.FirstOrDefault();

        //initialise filteredDynamicList
        IEnumerable<dynamic> filteredDynamicList = dynamicList;

        if (enumId != null)
        {
            //ExpandoObject implements IDictionary<string, object>, so cast as that to check what the fields are
            if (!((IDictionary<string, object>)first).ContainsKey(enumFieldName))
            {
                throw new KeyNotFoundException(string.Format("{0} is not a member of {1}", enumFieldName, genericList.GetType().GetGenericArguments()[0]));
            }

            //filter by the AddressStatus enum (as int)
            filteredDynamicList = dynamicList.Where(a => (int)((IDictionary<string, object>)a)[enumFieldName] == enumId.Value);
        }

        //convert from dynamic back to to generic
        var json = Newtonsoft.Json.JsonConvert.SerializeObject(filteredDynamicList);
        @return = Newtonsoft.Json.JsonConvert.DeserializeObject<List<T>>(json);

        return @return;
    }

Answer 1

先试试看能不能找到强类型解决方案（Expression/Func），然后再尝试其他方法（Reflection）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace ConsoleApplication9
{
class Program
{
    static void Main(string[] args)
    {

        var customers = Enumerable.Range(1, 10).Select(c => new Customer() { Id = c, Name = "Customer " + c });

        var filteredCustomers = StronglyNameFilter(customers, c => c.Id == 1);
        var filteredCustomers2 = StronglyNameFilter(customers, c => c.Name == "Customer 1");

        var filteredCustomers3 = ReflectionFilter(customers, "Id", 1);
        var filteredCustomers4 = ReflectionFilter(customers, "Name", "Customer 1");

        Console.ReadLine();
    }

    private static IEnumerable<T> StronglyNameFilter<T>(IEnumerable<T> collection, Func<T, bool> filter)
    {
        return collection.Where(filter).ToList();
    }
    private static IEnumerable<T> ReflectionFilter<T>(IEnumerable<T> collection, string property, object value)
    {
        if (collection.Count() == 0)
            return new List<T>();
        PropertyInfo pInfo = collection.First().GetType().GetProperty(property);

        return collection.Where(c => object.Equals(pInfo.GetValue(c), value)).ToList();
    }
}

public class Customer
{
    public string Name { get; set; }
    public int Id { get; set; }
}
}