List<T>多字段排序的一个通用类

本文中的方法旨在解决通用的问题，非常注重效率的地方，还应该针对具体的类去写排序方法。

废话不多说，直接上代码

具体使用场景：

• 要排序的类

 1         public class bb
 2         {
 3             public aa a { get; set; }
 4         }
 5 
 6         public class aa
 7         {
 8             public string index { get; set; }
 9             public string name { get; set; }
10 
11             public aa(string index, string name)
12             {
13                 this.index = index;
14                 this.name = name;
15             }
16         }

• 使用CommentComparer类排序

 1             List<bb> list = new List<bb>()
 2             {
 3                 new bb(){a = new aa("13", "35")},
 4                 new bb(){a = new aa("14", "35")},
 5                 new bb(){a = new aa("12", "35")},
 6                 new bb(){a = new aa("14", "12")},
 7             };
 8 
 9             CommentComparer<bb> comparer = new CommentComparer<bb>();
10             //comparer.IsAsc = true;
11             //comparer.IsProperty = true;
12             comparer.AddField("a.index");
13             comparer.AddField("a.name");
14 
15             list.Sort(comparer);

•  结果

CommentComparer类具体实现

    /// <summary>
    /// 排序类
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class CommentComparer<T> : IComparer<T>
    {
        /// <summary>
        /// 字段列表
        /// </summary>
        private List<string> fieldList;

        /// <summary>
        /// 排序字段序号
        /// </summary>
        private int index = 0;

        /// <summary>
        /// 正序
        /// </summary>
        public bool IsAsc { get; set; }

        /// <summary>
        /// 使用字段的属性排序
        /// <para>False:使用字段排序</para>
        /// </summary>
        public bool IsProperty { get; set; }

        public CommentComparer()
        {
            fieldList = new List<string>();
            IsAsc = true;
            IsProperty = true;
            index = 0;
        }

        /// <summary>
        /// 添加排序使用的字段
        /// </summary>
        /// <param name="fieldName"></param>
        public void AddField(string fieldName)
        {
            fieldList.Add(fieldName);
        }

        public int Compare(T x, T y)
        {
            if (x == null)
            {
                if (y == null)
                {
                    return 0;
                }

                return 1;

            }
            if (y == null)
            {
                return -1;
            }

            int result = -1;

            if (fieldList.Count < 1)
            { throw new FormatException("请添加排序所使用的字段!"); }
            if (index == 0 && !IsAsc)
            {
                T temp;
                temp = y;
                y = x;
                x = temp;
            }

            string[] field = fieldList[index].Split('.');

            dynamic p1 = GetValue<T>(x, field, 0);
            dynamic p2 = GetValue<T>(y, field, 0);

            result = Comparer<string>.Default.Compare(p1, p2);
            if (result == 0)
            {
                index++;
                if (fieldList.Count > index)
                { result = Compare(x, y); }
                index--;
            }
            return result;
        }

        /// <summary>
        /// 获取属性值
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="obj"></param>
        /// <param name="field"></param>
        /// <param name="i"></param>
        /// <returns></returns>
        private dynamic GetValue<T>(T obj, string[] field, int i)
        {
            dynamic result;

            Type t = typeof(T);

            if (IsProperty)
            {
                PropertyInfo propertyInfo = t.GetProperty(field[i]);
                result = propertyInfo.GetValue(obj, null);
            }
            else
            {
                FieldInfo fieldInfo = t.GetField(field[i]);
                result = fieldInfo.GetValue(obj);
            }

            if (i < field.Length - 1)
            {
                result = GetValue(result, field, ++i);
            }
            return result;
        }
    }