Select distinct values from a list using LINQ

Question

i want select distinct firstName's column from Database with linq
my class is:

public partial class user
{

    public string firstName{ get; set; }
    public string lastName{ get; set; }
    public int    dgree{ get; set; }
    public string class{ get; set; }
}

i using below code but return full list.

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

Distinct on a specific column? – Magnus Jul 13 '13 at 08:00 — Magnus, Jul 13 '13 at 08:00

score 2 · Accepted Answer · answered Jul 13 '13 at 07:53

To return distinct values from a list of custom objects you need to impelement the IEquatable<T> interface in the user class.

 public partial class user : IEquatable<user>
 {

public string firstName{ get; set; }
public string lastName{ get; set; }
public int    dgree{ get; set; }
public string class{ get; set; }

 public bool Equals(Product other)
{

   //check if the objects are the same based on your properties:
   //example 
    if (firstName == other.firstName) 
            return true; //then i assume they're equal and return true. You can check here all your properites that make an object unique. 

   return false; 
}

public override int GetHashCode()
 {
          // If Equals() returns true for a pair of objects  
// then GetHashCode() must return the same value for these objects. 
 }

  }`

More examples at : http://msdn.microsoft.com/en-us/library/bb348436.aspx

score 0 · Answer 2 · edited May 23 '17 at 10:28

0

The way you wrote it you get only exact duplicate lines cut. do you get any of them in your result ?

if you need to distinct on specific column check out this answer: Distinct By specific property

edited May 23 '17 at 10:28

Community

1
1

answered Jul 13 '13 at 07:50

Dani

14,639
11
62
110

Select distinct values from a list using LINQ

2 Answers2