Linq判断List>中的重复项

[活着生活]

导入Excel之前要检查一遍，看是否有重复的行等错误，多个模块有导入功能，我就想干脆写下面这样一个类，用来记录待导入文件中的错误：

    public class ImportLog
    {
        /// <summary>
        /// Excel行号
        /// </summary>
        public int RowID { get; set; }

        /// <summary>
        /// 当前行中每个单元格的值
        /// </summary>
        public List<object> FieldList { get; set; }

        /// <summary>
        /// 是否包含错误
        /// </summary>
        public bool HasError { get; set; }

        /// <summary>
        /// 错误信息
        /// </summary>
        public string ErrorMsg { get; set; }
    }

先拿“检查重复的行”来试试：

        public List<ImportLog> GetRepeatedRows(List<ImportLog> list = null)
        {
            if (list == null)
            {
                list = new List<ImportLog>()
                {
                    new ImportLog(){ RowID=1, FieldList=new List<object>(){"1","11","111"}, ErrorMsg=""},
                    new ImportLog(){ RowID=2, FieldList=new List<object>(){"1","11","111"}, ErrorMsg=""},
                    new ImportLog(){ RowID=3, FieldList=new List<object>(){"1","11","111","1111"}, ErrorMsg=""},
                    new ImportLog(){ RowID=4, FieldList=new List<object>(){"1","11","111","1112"}, ErrorMsg=""},
                    new ImportLog(){ RowID=5, FieldList=new List<object>(){"1","11","112","1121"}, ErrorMsg=""},
                    new ImportLog(){ RowID=6, FieldList=new List<object>(){"1","11","112","1121"}, ErrorMsg=""},
                    new ImportLog(){ RowID=7, FieldList=new List<object>(){"1","12","121","1211"}, ErrorMsg=""},
                    new ImportLog(){ RowID=8, FieldList=new List<object>(){"1","12","122","1221"}, ErrorMsg=""},
                    new ImportLog(){ RowID=9, FieldList=new List<object>(){"1","13","131","1311"}, ErrorMsg=""},
                    new ImportLog(){ RowID=10, FieldList=new List<object>(){"2","21","211","2111"}, ErrorMsg=""},
                    new ImportLog(){ RowID=11, FieldList=new List<object>(){"2","21","211","2111"}, ErrorMsg=""},
                    new ImportLog(){ RowID=11, FieldList=new List<object>(){"2","21","211","2111"}, ErrorMsg=""},
                };
            }
            //方式1：成功，但效率貌似不高
            //var ret1 = list.FindAll(a => list.FindAll(b => b.FieldList.Intersect(a.FieldList).Count() == a.FieldList.Count).Count > 1);

            //方式2：group by m.FieldList into g 失败
            var ret2 = (from t in list
                        where (
                         from d in
                             (
                                 from m in list
                                 group m by m.FieldList into g
                                 where g.Count() > 1
                                 select g
                                 )
                         select d.Key
                        ).Contains(t.FieldList)
                        select t).ToList();
            var count = ret2.Count;//count=0 ……

            return ret2;

        }

各位大神，谁能给优化一下方式1，再给改改方式2？
拜谢！

呃，准备下班了，明天上午来了给分，见谅……

[q107770540]

var ret2=list.GroupBy(l=>string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()))
			 .Where(g=>g.Count()>1);

[活着生活]

[Quote=引用 1 楼 的回复:]

C# code
var ret2=list.GroupBy(l=>string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()))
.Where(g=>g.Count()>1);
[/Quote]
谢了，是个思路。
呃，不过，我是想最终得到一个List<ImportLog>，按照你这样GroupBy()之后得到的是一个IEnumerable<IGrouping<string, ImportLog>>，然后还要遍历list。有个更精简点的办法没？

[sad_4978]

我尝试也写了一个，不知道符不符合要求。

var result = list.GroupBy(L => L.RowID).Select(G => G.First()).ToList();

[q107770540]

[Quote=引用 1 楼 的回复:]

C# code
var ret2=list.GroupBy(l=>string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()))
.Where(g=>g.Count()>1);
[/Quote]
var ret2=(from l in list
group l by string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()) into g
from x in g
select x).ToList();

[活着生活]

[Quote=引用 3 楼 的回复:]

我尝试也写了一个，不知道符不符合要求。

var result = list.GroupBy(L => L.RowID).Select(G => G.First()).ToList();
[/Quote]
呃，忘了说明一下了：List<object> FieldList，代表的是Excel一行中的单元格，只要这个属性相同，就视为重复的行，行号只是用来标记，不计入判断……
而且，既然是检查Excel文件里的重复的行，那么不能只是把重复的内容找到，还要找到文件里都有哪些行是重复的。
所以，你这个似乎可以改一下：

            var listRepeat = list.GroupBy(L => L.FieldList).Select(G => G.First()).ToList();
            listRet.FindAll(l => listRepeat.FindAll(r => l.FieldList.SequenceEqual(r.FieldList)).Count > 1);

[活着生活]

我一朋友还给了另外一种写法，但是，效率更低……

            var listRet = list.Where(m => list.Count(c => c.FieldList.SequenceEqual(m.FieldList)) > 1).ToList();

[活着生活]

[Quote=引用 4 楼 的回复:]

引用 1 楼 的回复:

C# code
var ret2=list.GroupBy(l=>string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()))
.Where(g=>g.Count()>1);

var ret2=(from l in list
group l ……
[/Quote]
Tim兄，你这个不太符合我的规则啊，我是要把【重复的行】取出来……
所以：

            listRet = (from l in list
                        group l by string.Join(",", l.FieldList.OrderBy(x => x).Select(x => x.ToString()).ToArray()) into g
                        where g.Count() > 1//有“重复”的行
                        from x in g
                        select x).ToList();

然后，另外那个有点错，我也改了改：

            var listRepeat = list.GroupBy(L => string.Join(",", L.FieldList.OrderBy(x => x))).Where(c => c.Count() > 1).Select(G => G.First()).ToList();
            listRepeat.ForEach(m => listRet.AddRange(list.FindAll(r => r.FieldList.SequenceEqual(m.FieldList))));

呃，后面如果没人回复的话，我就再说不了话了吧？
那如果再没人来，就结贴了，上面两位兄弟都有分

[q107770540]

取出所有重复的行：
var ret2=(from l in list
group l by string.Join(",",l.FieldList.OrderBy(x=>x).Select(x=>x.ToString()).ToArray()) into g
where g.Count()>1
from x in g
select x).ToList();

[活着生活]

ok，结贴！
多谢Tim兄和sad_4978兄捧场！