Remove Duplicate based on column value-linq

Question

i have many to many relationship between employee and group. following linq statement

int[] GroupIDs = {6,7};


var result = from g in umGroups
    join empGroup in umEmployeeGroups on g.GroupID equals empGroup.GroupID
    where  GroupIDs.Contains(g.GroupID)                     
    select new {  GrpId = g.GroupID,EmployeeID = empGroup.EmployeeID };

returns groupid and the employeeid. and result is

GrpId  | EmployeeID
6      |   18
6      |   20  
7      |   19
7      |   20

I need to remove the rows for which the employeeid is repeating e.g. any one of the row with employeeid= 20
Thanks

What would make it remove the last row rather than the one with GrpId=6? — Jon Skeet
– Jon Skeet, Commented Aug 10, 2010 at 6:10
ok, i need result with distinct Employeeids any one can be removed — Tassadaque
– Tassadaque, Commented Aug 10, 2010 at 6:13

d219 · Accepted Answer · 2018-02-09 12:48:19Z

42

Okay, if you don't care which employee is removed, you could try something like:

var result = query.GroupBy(x => x.EmployeeId)
                  .Select(group => group.First());

You haven't specified whether this is in LINQ to SQL, LINQ to Objects or something else... I don't know what the SQL translation of this would be. If you're dealing with a relatively small amount of data you could always force this last bit to be in-process:

var result = query.AsEnumerable()
                  .GroupBy(x => x.EmployeeId)
                  .Select(group => group.First());

At that point you could actually use MoreLINQ which has a handy DistinctBy method:

var result = query.AsEnumerable()
                  .DistinctBy(x => x.EmployeeId);

edited Feb 9, 2018 at 12:48

d219

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answered Aug 10, 2010 at 6:30

Jon Skeet

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3 Comments

Tassadaque Over a year ago

just for curiosity! what if i want to remove specific row based on groupid.

Jon Skeet Over a year ago

@Tassadaque: You'd have to give more details about what you want - but you could potentially use Except or Where.

d219 Over a year ago

That's a great extension!

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