c# list排序的三种实现方式

2012-10-30 雨辰 C#

首先先介绍一下平时最常用的几种排序方法。

第一种:实体类实现IComparable接口,而且必须实现CompareTo方法

实体类定义如下:

 

class Info:IComparable
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public int CompareTo(object obj) {
            int result;
            try
            {
                Info info = obj as Info;
                if (this.Id > info.Id)
                {
                    result = 0;
                }
                else
                    result = 1;
                return result;
            }
            catch (Exception ex) { throw new Exception(ex.Message); }
        }
    }


调用方式如下,只需要用sort方法就能实现对list进行排序。
private static void ReadAccordingCompare() {
            List<Info> infoList = new List<Info>();
            infoList.Add(
                new Info() { Id = 1, Name = "abc" });
            infoList.Add(new Info() { Id = 3, Name = "rose" });
            infoList.Add(new Info() { Id = 2, Name = "woft" });
               infoList.Sort();
            foreach (var item in infoList)
            {
                Console.WriteLine(item.Id + ":" + item.Name); 
            }
        }

第二种方法:linq to list进行排序

运用linq实现对list排序,在实体类定义的时候就不需用实现IComparable接口,调用方式如下:

private static void ReadT(string str) {
            List<Info> infoList = new List<Info>();
            infoList.Add(
                new Info() { Id = 1, Name = "woft" });
            infoList.Add(new Info() { Id=3,Name="rose"});
            infoList.Add(new Info() { Id = 2, Name = "abc" });
            Console.WriteLine("ReadT*********************");
            IEnumerable<Info> query = null;
            query = from items in infoList orderby items.Id select items;
            foreach (var item in query)
            {
                Console.WriteLine(item.Id+":"+item.Name);
            }
        }
 
 

但是上面两种方式都只能对一个实体属性排序,如果对不同的属性排序的话只能写很多的if进行判断,这样显得很麻烦。

且看下面的方式实现根据传入参数进行排序。

 

private static void ListSort(string field,string rule)
        {
            if (!string.IsNullOrEmpty(rule)&&(!rule.ToLower().Equals("desc")||!rule.ToLower().Equals("asc")))
            {
                try
                {
                    List<Info> infoList = GetList();
                    infoList.Sort(
                        delegate(Info info1, Info info2)
                        {
                            Type t1 = info1.GetType();
                            Type t2 = info2.GetType();
                            PropertyInfo pro1 = t1.GetProperty(field);
                            PropertyInfo pro2 = t2.GetProperty(field);
                            return rule.ToLower().Equals("asc") ?
                                pro1.GetValue(info1, null).ToString().CompareTo(pro2.GetValue(info2, null).ToString()) :
                                pro2.GetValue(info2, null).ToString().CompareTo(pro1.GetValue(info1, null).ToString());
                        });
                    Console.WriteLine("*****ListSort**********");
                    foreach (var item in infoList)
                    {
                        Console.WriteLine(item.Id + "," + item.Name);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            } Console.WriteLine("ruls is wrong");

        }
 

 

调用方式:

ListSort("Name","desc");//表示对Name进行desc排序 ListSort("Id","asc");//表示对Id进行asc排序。如此如果参数很多的话减少了很多判断。

 

如果有更好的方法欢迎提出,共同学习………..

后续:受一位留言着的提醒,在用反射实现多字段排序时只需一次反射,多余的一次放而会影响性能,现更新如下:

private static void ListSort(string field,string rule)
        {
            if (!string.IsNullOrEmpty(rule) && (rule.ToLower().Equals("desc") || rule.ToLower().Equals("asc")))
            {
                try
                {
                    List<Info> infoList = GetList();
                    infoList.Sort(
                        delegate(Info info1, Info info2)
                        {
                            Type t = typeof(Info);
                            PropertyInfo pro = t.GetProperty(field);
                            return rule.ToLower().Equals("asc") ?
                                pro.GetValue(info1, null).ToString().CompareTo(pro.GetValue(info2, null).ToString()) :
                                pro.GetValue(info2, null).ToString().CompareTo(pro.GetValue(info1, null).ToString());
                        });
                    Console.WriteLine("*****ListSort**********");
                    foreach (var item in infoList)
                    {
                        Console.WriteLine(item.Id + "," + item.Name);
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            }
            else
                Console.WriteLine("ruls is wrong");
        }
 

标签: C#

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