过滤实体,然后对动态字段进行排序

Question

我正在尝试首先过滤一组产品,然后订购它们

  (repository.GetAllProducts()
     .Where(x=>x.Naam.Contains("filter")) as ObjectQuery<Product>)
     .FunkyOrder<Product>(sortfield,sortdirection)

使用Extension方法:

 public  static IEnumerable<T> FunkyOrder<T>(this ObjectQuery<T> input, string fieldname = "Id", string sortdirection = "asc")
        {            
            switch (sortdirection)
            {
                case "dsc":
                case "desc":
                    return input.OrderBy("it." + fieldname + " DESC");
                default:
                    return input.OrderBy("it." + fieldname);

            }
        }

(我的Repository的GetAllProducts()返回一个IEnumerable

这个FunkyOrder方法应该可以工作,但是 - 作为ObjectQuery - cast返回NULL

我只能使用带有ObjectQuery的FunkyOrder,因为这似乎是唯一支持那些"it.FieldName"查询的东西.

如果我将 - as - notation更改为常规演员,我得到:

 Unable to cast object of type 'WhereEnumerableIterator`1[MySecretNameSpace.Product]' to type 'System.Data.Objects.ObjectQuery`1[MySecretNameSpace.Product]'.

有没有办法让这项工作或者我会被迫在过滤之前使用排序,或者为我的排序编写一个带有lambda表达式的巨型开关？

Answer 1

这实际上是一个试图解决的巨大头痛; 但最终,它实际上很容易通过一些hackishness和反思来完成:

public class Program
{
    public class SomeClass
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    static void Main(string[] args)
    {
        List<SomeClass> sample = new List<SomeClass>
        {
            new SomeClass { Id = 4, Name = "ABC" },
            new SomeClass { Id = 1, Name = "XYZ" },
            new SomeClass { Id = 2, Name = "JKL" }
        };

        var result = sample.OrderByDynamic("Name", OrderDirection.Ascending).ToList();

        result.ForEach(x => Console.WriteLine("Id: " + x.Id + " | Name: " + x.Name));

        Console.ReadKey();
    }
}

public enum OrderDirection
{
    Ascending,
    Descending
}

public static class LinqExtensions
{
    public static IEnumerable<T> OrderByDynamic<T>(this IEnumerable<T> source, string propertyName, OrderDirection direction = OrderDirection.Ascending)
    {
        if(direction == OrderDirection.Ascending)
            return source.OrderBy(x => x.GetType().GetProperty(propertyName).GetValue(x, null));
        else
            return source.OrderByDescending(x => x.GetType().GetProperty(propertyName).GetValue(x, null));
    }
}

这个例子在测试情况下对我有用; 我可以提供属性名称,并指定排序方向,它工作得很好.只需这样打电话:

yourEnumerable.OrderByDynamic("YourPropertyName");
yourEnumerable.OrderByDynamic("YourPropertyName", OrderDirection.Descending);

请享用!