使用LINQ从列表中选择不同的数据

Question

I have a list which contains some properties and list. I want to select the unique records based on the property of inner list how can i achieve it using LINQ Example List

{item1 = 1, item2=2,list{a1=l1,a2=l2,a3=l5},item3 =3}
{item1 = 21, item2=21,list{a1=l11,a2=l2,a3=l3},item3 =3}
{item1 = 31, item2=22,list{a1=l12,a2=l2,a3=l3},item3 =3}
{item1 = 41, item2=23,list{a1=l1,a2=l2,a3=l3},item3 =3}

I want to select the record which has distinct value of property "a1".If I found duplicate value of "a1" then i will compare value "a3" != "l5"

Expected Result:

{item1 = 21, item2=21,list{a1=l11,a2=l2,a3=l3},item3 =3}
{item1 = 31, item2=22,list{a1=l12,a2=l2,a3=l3},item3 =3}
{item1 = 41, item2=23,list{a1=l1,a2=l2,a3=l3},item3 =3}

Answer 1

First you want to GroupBy on your inner list a1 and then select within that grouping for a3!="l5".

List<foo> col = new List<foo>();
List<string> tmp = new List<string> {"l1","l2","l5"};
col.Add(new foo {item1 = 1, item2=2,lst=tmp,item3 =3});
tmp = new List<string> {"l11","l2","l3"};
col.Add(new foo {item1 = 21, item2=21,lst=tmp,item3 =3});
tmp = new List<string> {"l12","l2","l3"};
col.Add(new foo {item1 = 31, item2=22,lst=tmp,item3 =3});
tmp = new List<string> {"l1","l2","l3"};
col.Add(new foo {item1 = 41, item2=23,lst=tmp,item3 =3});

var qry = col.GroupBy(i => i.lst[0]).Select(g => g.Where(j => j.lst[2]!="l5"));

If there are multiple duplicates where your a3 is not "l5" you will get all of them so you may need to filter on something else if this is not desired.

Answer 2

class Log
{
    public int DoneByEmpId { get; set; }
    public string DoneByEmpName { get; set; }

  }

public class Class1
{
    static void Range()
    {
        var array = new List<Log>() {new Log() {DoneByEmpId = 1,DoneByEmpName = "Jon"},
            new Log() { DoneByEmpId = 1, DoneByEmpName = "Jon" } ,
            new Log() { DoneByEmpId = 2, DoneByEmpName = "Max" },
            new Log() { DoneByEmpId = 2, DoneByEmpName = "Max" },
            new Log() { DoneByEmpId = 3, DoneByEmpName = "Peter" }};

        var ordered =
            array.GroupBy(x => x.DoneByEmpId).ToList().Select(x => x.FirstOrDefault()).OrderBy(x => x.DoneByEmpName);
        foreach (var item in ordered)
        {
            Console.WriteLine(item.DoneByEmpName);
        }
    }
}

Result :
Jon
Max
Peter