Remove objects with a duplicate property from List in c#

Question

I Have a list and I want to create a new one without records with duplicate values

public List<links> results = new List<links>();
public List<links> final_results = new List<links>();
public class links
{
    public string url { get; set; }
    public string title { get; set; }
    public string description { get; set; }
    public int place { get; set; }
}

results gets it's values during code. Same record may occur with unique Place property but other properties are the same. I want to ommit duplicate records which have duplicate value in the url, title and description. I wrote this code but nothing changed:

     final_results = results .GroupBy(n => n.url).Select(g => g.FirstOrDefault()).ToList();

but when I bind my repeator to this new list nothing has changed. how can I ommit this duplicte value?

I don't believe that nothing has changed because it should work. But it's not clear if you only want to check the single property `url` or if the combination of the three properties `url`,`title `, `description` is equal. — Tim Schmelter, Sep 27 '16 at 14:18
Can you post some example data? Do you check the contents of `final_results` or something else? If you check an HTML control you may be binding to the wrong data. — Panagiotis Kanavos, Sep 27 '16 at 14:19
@mary, I think what you want is a [DistinctBy() Property](http://stackoverflow.com/questions/489258/linqs-distinct-on-a-particular-property) extension method. — jmbmage, Sep 27 '16 at 14:20
@TimSchmelter I think it is not important which property I check because just Place property is unique . — mary, Sep 27 '16 at 14:29
@PanagiotisKanavos i use a Repeater and bind it to the list I want to ommit duplicate records — mary, Sep 27 '16 at 14:29
@jmb.mage distinctby() property is used for records which have all properties the same but in my case I should check some properties — mary, Sep 27 '16 at 14:29
You could write a class that implements IEqualityComparer by comparing on the properties you are interested in, then use the Linq Distinct() overload that takes the comparer as a parameter: https://msdn.microsoft.com/en-us/library/bb338049(v=vs.110).aspx — Joe, Sep 27 '16 at 14:39

score 6 · Accepted Answer · answered Sep 27 '16 at 14:21

6

If you want to suppress records with equality in 3 preperties url,titleand description, you have to group by all of them:

final_results = results.GroupBy(n => new {n.url, n.description, n.title})
                       .Select(g => g.FirstOrDefault()).ToList();

answered Sep 27 '16 at 14:21

fubo

44,811
17
103
137

@mary you're binding the repeater to `Repeater.DataSource = final_results; Repeater.DataBind();` ? – fubo Sep 27 '16 at 14:38
@fubo as u said Rep.DataSource = final_results; Rep.DataBind(); – mary Sep 27 '16 at 14:46

eocron · Answer 2 · 2016-09-27T14:44:58.263

0

Umm, you can just do:

var results = results.DistinctBy(x=> x.url);

Or if you want to exclude by multiple fields, simpliest is this:

var results = results.DistinctBy(x=> x.url + "," + x.title + "," + x.description);

If you want to do it properly - just override Equal and GetHashCode methods of your object and put your values in HashSet.

For DistinctBy to work, you can increase your .NET version or just use MoreLINQ.

edited Sep 27 '16 at 14:44

answered Sep 27 '16 at 14:38

eocron

6,885
1
21
50

tnx exactly I cant use DistinctBy for results – mary Sep 27 '16 at 14:49
Then just write your own. There is plenty implementations here on stackoverflow. Including slow comparing distinction. – eocron Sep 27 '16 at 14:51

score 0 · Answer 3 · answered Sep 27 '16 at 15:10

0

try using Except extension method over the Links

final_results = results.Except(--duplicate criteria--)

answered Sep 27 '16 at 15:10

Pranay

432
4
14

what should i write in criteria ? i want to ommit duplicate values? – mary Sep 27 '16 at 15:16

Remove objects with a duplicate property from List in c#

3 Answers3