How to get distinct values from a list?

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I have a list that 4 objects with three fields has the following
The fields are string day, int Id and string time

[0] Sunday  1    9:00 to 10:00
[1] Monday  1    9:00 to 10:00
[2] Sunday  1    9:00 to 10:00
[3] Monday  1    9:00 to 10:00

I don't want the output to have repeated values, so the output should be like this

[0] Sunday  1    9:00 to 10:00
[1] Monday  1    9:00 to 10:00

What I have tried:

I tried list.Distinct(); but it's output remained the same.

Posted 12-May-20 3:02am

Member 14800672

Updated 12-May-20 7:06am

v3

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MadMyche 12-May-20 10:29am

Please use the Improve Question widget and add in the Class definition for the object in question

Member 14800672 12-May-20 11:03am

I added the fields types in the question
String Day; example: Sunday
Int id; example: 1
String time; example: 9:00 to 10:00

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Richard Deeming · Answer 1 · 2020-05-12T05:08:00

Solution 1

Your object needs to implement IEquatable<T>:
IEquatable<T> Interface (System) | Microsoft Docs[^]

Or you need to provide a custom IEqualityComparer<T> to the Distinct method:
IEqualityComparer<T> Interface (System.Collections.Generic) | Microsoft Docs[^]

Posted 12-May-20 5:08am

Richard Deeming

Comments

Maciej Los 12-May-20 11:44am

5ed!

Maciej Los · Answer 2 · 2020-05-12T07:07:00

Another way (as an alternative to solution #1) is to use GroupBy + Select

C#

var distinctValues = listofvalues
    .GroupBy(x => new {Day = x.Day, Id = x.Id, Time = x.Time})
    .Select(grp => grp.First())
    .ToList();

Shorter version of above:

C#

var distinctValues = listofvalues
    .GroupBy(x => new {Day = x.Day, Id = x.Id, Time = x.Time}, (key, x) => x.FirstOrDefault())
    .ToList();

or use ToLookup()[^]

C#

var distincts = listofvalues
		.ToLookup(c => new {Day = x.Day, Id = x.Id, Time = x.Time})
		.Select(g => g.First())
		.ToList();