如何在基本类型(如 IPerson 接口)的集合上运行动态 LINQ 查询,但访问特定于实现的属性(如 Age)。
我可以确定集合中的所有项目都是相同的,即查看第一种类型,我可以假设其他类型相同。
我需要一个可以将过滤器应用于不同集合的 UI,用户可以看到所有可用的属性。
这是我想做的一个例子,Expression.Call 方法抛出一个异常:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Linq.Dynamic;
using DynamicExpression = System.Linq.Dynamic.DynamicExpression;
namespace DynamicLinqTest
{
public interface IPerson
{
string Name { get; set; }
}
public class Person : IPerson
{
public string Name { get; set; }
public int Age { get; set; }
public double Income { get; set; }
}
class Program
{
public static IEnumerable<Person> GetPersons()
{
yield return new Person { Name = "Sam", Age = 26, Income = 50000 };
yield return new Person { Name = "Rick", Age = 27, Income = 0 };
yield return new Person { Name = "Joe", Age = 45, Income = 35000 };
yield return new Person { Name = "Bill", Age = 31, Income = 40000 };
yield return new Person { Name = "Fred", Age = 56, Income = 155000 };
}
static void Main(string[] args)
{
IEnumerable<IPerson> persons = GetPersons();
var personsQueriable = persons.AsQueryable();
//what I would like to do:
// personsQueriable.Where("Age > 30");
var l = DynamicExpression.ParseLambda(persons.First().GetType(), typeof(bool), "Age > 30");
var filtered = personsQueriable.Provider.CreateQuery(
Expression.Call(
typeof(Queryable), "Where",
new Type[] { persons.First().GetType() },
personsQueriable.Expression, Expression.Quote(l)));
ObjectDumper.Write(filtered);
Console.Read();
}
}
}