如何使用 List<String> 变量过滤强类型列表

Question

我需要过滤一个 StaffingPositionsDataContract 类型的强类型列表，以及另一个过滤器名称和值列表。我有这两个列表：

    List<SerializedForm> deserializedObject = JsonConvert.DeserializeObject<List<SerializedForm>>(searchFilters).Where(x => !string.IsNullOrEmpty(x.value) && !string.Equals(x.value.ToUpper(), "ALL")).ToList();
    List<StaffingPositionsDataContract> staffingPositionResponse = new StaffingPositionsDataContract().LoadMockData();

deserializedObject 有 2 个属性。 1：“名称”，2：“值”。这些属性需要能够过滤几个具有不同属性的不同类。如果当前正在过滤的 StaffingPositionsDataContract 是一个字符串，但不是 int、decimal 或 float，我有一个方法可以工作。以下是我使用的仅适用于字符串过滤器的内容。

  private static List<T> _GetFilteredList<T, U>(IList<T> ListToFilter, string PropertyToFilterOn, List<U> FilterValues)
    {
        ParameterExpression p = Expression.Parameter(typeof(T), "x");

        Func<T, U> select = Expression.Lambda<Func<T, U>>(
            Expression.Property(p, PropertyToFilterOn), p).Compile();

        return ListToFilter.Join(FilterValues, select, u => u, (t, u) => t).ToList();
    }

这是如何调用的：

 var filteredPositions = staffingPositionResponse;
        deserializedObject.ForEach(delegate(SerializedForm filters)
        {
            filteredPositions = _GetFilteredList<StaffingPositionsDataContract, string>(staffingPositionResponse, filters.name, new List<string> { filters.value });
        });

任何人都知道我可以如何使用反序列化对象来过滤 staffingPositionResponse 类吗？

Answer 1

这是一个执行类似操作的控制台应用程序。您必须评估如何从应用程序的表单中获取正确的 json 序列化。出于测试目的，我只是将 Dictionary 强制转换为 json 字符串。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Newtonsoft.Json;
using System.Reflection;

namespace FilterLists
{
    public class Program
    {
        static void Main(string[] args)
        {
            // set up the bunk json
            var filters = new Dictionary<string, object>();
            filters.Add("PositionId", "12345");
            string json = JsonConvert.SerializeObject(filters);
            // what's it look like as a string?
            Console.WriteLine(json);

            // take the json string and stuff it to our method.
            var result = GetStaffingPosition(json);
            Console.WriteLine(result.Count);
        }

    public static List<StaffingPositionsDataContract> GetStaffingPosition(string searchFilters)
    {
        var filters = JsonConvert.DeserializeObject<Dictionary<string, object>>(searchFilters).ToList();
        var contracts = StaffingPositionsDataContract.LoadMockData();

        List<StaffingPositionsDataContract> result = new List<StaffingPositionsDataContract>();

        foreach (var filter in filters)
        {
            foreach (var contract in contracts)
            {
                PropertyInfo info = typeof(StaffingPositionsDataContract).GetProperty(filter.Key);
                var propType = info.PropertyType;

                if (info.GetValue(contract, null).Equals(Convert.ChangeType(filter.Value, propType)))
                {
                    result.Add(contract);
                }
            }
        }

        return result;
    }
}


[Serializable]
public class StaffingPositionsDataContract
{
    public int PositionId { get; set; }
    public string Series { get; set; }
    public string BFY { get; set; }
    public string BudgetStatus { get; set; }
    public string DutyStation { get; set; }
    public string OrgLocation { get; set; }
    public string BudgetingEntity { get; set; }
    public string FieldName { get; set; }

    public static List<StaffingPositionsDataContract> LoadMockData()
    {
        List<StaffingPositionsDataContract> staffingposition = new List<StaffingPositionsDataContract>()
        {
            new StaffingPositionsDataContract() {PositionId = 12345, Series="", BFY="FY2010", BudgetStatus="Actual", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {PositionId = 67891, Series="", BFY="FY2011", BudgetStatus="Actual", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {PositionId = 12345, Series="", BFY="FY2010", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {PositionId = 67892, Series="", BFY="FY2011", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""},
            new StaffingPositionsDataContract() {PositionId = 987654, Series="", BFY="FY2010", BudgetStatus="Projected", DutyStation="", OrgLocation="", BudgetingEntity=""}
        };
        return staffingposition;
    }
}
}

Answer 2

请注意，仅当您在编译时无法知道属性名称时才应使用此方法；但以下似乎有效：

public static IEnumerable<T> WhereAny<T, U>(
    this IEnumerable<T> ListToFilter, string PropertyToFilterOn, List<U> FilterValues)
{
    ParameterExpression p = Expression.Parameter(typeof(T), "x");
    var methodCall = Expression.Call(            
        Expression.Constant(FilterValues, typeof(List<U>)),
        typeof(List<U>).GetMethod("Contains"),
        Expression.PropertyOrField(p, PropertyToFilterOn)
    );
    return ListToFilter.Where(Expression.Lambda<Func<T,bool>>(methodCall, p).Compile());
}