c# - 动态 Linq 中的按位排序

Question

我需要能够在动态 linq 中执行基于字符串的按位 .OrderBy 。

items = items.OrderBy(x => (x.Permissions & 65536) != 0);

对比

items = items.Where("1==1" + where).OrderBy("Permissions & 65536 != 0")

这甚至可能吗？我在下载 (CSharpSamples.zip\LinqSamples\DynamicQuery) 中没有看到任何按位运算符的示例。我什么都做不了，也找不到任何例子。帮助！

Answer 1

您可以根据字符串输入对数据库的列重新排序。下面的代码已经过测试并且可以工作。

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;

namespace ConsoleApplication75
{
    class Program
    {
         static void Main(string[] args)
        {
            //u = user
            //g = group
            //s = system
            //r = read
            //w = write
            //e = execute

            //array below represents the normal position of the permissions
            List<string> permissions = new List<string>() { "ue", "uw", "ur", "ge", "gw", "gr", "se", "sw", "sr" };

            //below is the order we actually want
            List<string> sortOrder = new List<string>() { "ue", "ge", "se", "uw", "gw", "sw", "ur", "gr", "sr" };

            List<cFile> files = new List<cFile>() {
                new cFile() { name = "A", permission = 0x001},
                new cFile() { name = "B", permission = 0x002},
                new cFile() { name = "C", permission = 0x004},
                new cFile() { name = "D", permission = 0x008},
                new cFile() { name = "E", permission = 0x010},
                new cFile() { name = "F", permission = 0x020},
                new cFile() { name = "G", permission = 0x040},
                new cFile() { name = "H", permission = 0x080},
                new cFile() { name = "I", permission = 0x100}
            };


            //now reorder the columns
             var tempData = files.Select(x => new { files = x, shiftedPermissions =  Enumerable.Range(0, 9).Select(y => (permissions.IndexOf(sortOrder[y]) - y >= 0) ?
                (1 << y) & (x.permission >> (permissions.IndexOf(sortOrder[y]) - y)) :
                (1 << y) & (x.permission << (y - permissions.IndexOf(sortOrder[y])))).Sum()
             }).ToList();

             List<cFile> sortedPermissions = tempData.OrderBy(x => x.shiftedPermissions).Select(x => x.files).ToList();

        }

    }
    public class cFile
    {
        public string name { get; set; }
        public UInt32 permission { get; set; }
    }


}