How to get the distinct preferred value in LINQ

Question

0.00/5 (No votes)

See more:

Hi Consider I am having a data structure

id Name Date
1 Alex 2-Apr-2013
2 Dale 3-Mar-2012
3 Alex 5-Apr-2013

I am having a class with similar data structure. My question is how would I extract the values with distinct name and if the name are similar then I have to get the one with the latest date.

For example the result has to be
id Name Date
3 Alex 5-Apr-2013 (=>Not the data with 2-Apr)
2 Dale 3-Mar-2012

I can get the distinct values by using IEqualityComparer but I don't know how to get the preferred data.??

Posted 10-Feb-14 18:10pm

Prasaad SJ

Add a Solution

Comments

[no name] 11-Feb-14 0:59am

Have you has a look at this link?

http://msdn.microsoft.com/en-us/library/ms131190(v=vs.100).aspx

Prasaad SJ 11-Feb-14 1:29am

Hi,
Thanks for your reply. I am quiet comfortable with using EqualityComparator. Buy my question is if 2 rows are equal then i have get the row with the latest date. How could that be possible

[no name] 11-Feb-14 4:05am

so you got the answer and your question is how you got that answer, correct? that's what i understood from your last reply.if what i have understood was correct. you would have added the item in the list in such a way or you would have used some sorting logic before adding to that list. please correct me if i was wrong.

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

RK Tailor · Answer 1 · 2014-02-11T01:54:00

Please refer this code ...I created sample according to your requirement.

C#

public class SampleClass
    {
        public int ID { get; set; }
        public string  Name { get; set; }
        public DateTime Date { get; set; }

    }

Then following is query to get records:

XML

var sampleLst=new List<SampleClass>{
           new SampleClass{ ID=1,Name="Alex",Date=DateTime.Now},
           new SampleClass{ID=2,Name="Dale",Date=DateTime.Now},
           new SampleClass{ID=3,Name="Alex",Date=DateTime.Now.AddDays(1)}
        };
           var result = from t in sampleLst
                        group t by t.Name into g
                        select g.OrderByDescending(x=>x.Date).FirstOrDefault();

george4986 · Answer 2 · 2014-02-10T21:29:00

Solution 1

plz try this code.

////////sourceDt -datatable to be filtered
/////////Name,Date-table field
/////////resultDt-output datatable
////////assuming ur fields Name,Date,id fields on table are string datatype(VARCHAR)

C#

var distinctData = from c in sourceDt.AsEnumerable()
group c by c.Field<string>("Name") into grp
select grp.OrderByDescending(c => Convert.ToDateTime(c.Field<string>("Date")) ).FirstOrDefault();
DataTable resultDt = distinctData.CopyToDataTable();

Posted 10-Feb-14 21:29pm

george4986

Updated 10-Feb-14 21:30pm

v2

Comments

Prasaad SJ 11-Feb-14 4:24am

Basically you are arranging the list in descending order and then you are using a distinct value. This is how I am using now and it works well as the first row in the duplicate rows returned everytime.

Thanks.

george4986 11-Feb-14 5:28am

first grouping with name then sorting in descending date after that selecting first record

SharmaVipin · Answer 3 · 2014-02-10T21:55:00

Solution 2

var query = (from user _db.Users select user).Distinct().OrderBy(u=>u.firstName).ToList();

Posted 10-Feb-14 21:55pm

SharmaVipin

Comments

Prasaad SJ 11-Feb-14 4:21am

Hi Vipin,
This will return the distinct values and then order So it wont be the solution .

How to get the distinct preferred value in LINQ

3 solutions

Solution 3

Solution 1

Solution 2

Add your solution here

Preview 0

Existing Members

...or Join us