Distinct elements in LINQ

Question

I have a situation where i display a list of products for a customer. So, there are two kinds of products. So, if customer is registerd to two products, then both the products get displayed. So, I need to display distinct rows. I did this:

   var queryProducts = DbContext.CustomerProducts.Where(p => p.Customers_Id ==  
                                            customerID).ToList().Select(r => new
                           {
                               r.Id,
                               r.Products_Id,
                               ProductName = r.Product.Name,
                               ShortName = r.Product.ShortName,
                               Description = r.Product.Description,
                               IsActive = r.Product.IsActive

                           }).Distinct();

In this, customerID is the value that i get from dropdownlist. However, it still displays the same row twice. So, can you please let me know how i can display only distinct records.

On what property you want the Distinct to act on? – Ramesh May 07 '12 at 03:53 — Ramesh, May 07 '12 at 03:53

score 3 · Accepted Answer · edited May 23 '17 at 10:34

The most likely reasons could be that Distinct when called with no parameter by default compares all the public properties for equality. I suspect your Id is going to be unique. Hence the Distinct is not working for you.

You can try something like

myCustomerList.GroupBy(product => product.Products_Id).Select(grp => grp.First());

I found this as answers to

McGarnagle · Answer 2 · 2012-05-07T03:53:56.903

1

You can write an implementation of IEqualityComparer<CustomerProduct>. Once you've got that, then you can use this:

DbContext.CustomerProducts.Where(p => p.Customers_Id == customerId)
    .ToList()
    .Distinct(new MyComparer())
    .Select(r => new {
    // etc.

public class MyComparer : IEqualityComparer<CustomerProduct>
{
    // implement **Equals** and **GetHashCode** here
}

Note, using this anonymous comparer might work better for you, but it compares all properties in the anonymous type, not just the customer ID as specified in the question.

edited May 07 '12 at 03:53

answered May 07 '12 at 03:48

McGarnagle

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Can that be done as an anonymous function without the separate method @dbaseman? – dumbledad Dec 10 '12 at 17:25
1

@dumbledad there isn't :(. I don't know of any way to do it inline using an anonymous function. http://stackoverflow.com/q/191013/1001985 – McGarnagle Dec 10 '12 at 17:30

score 1 · Answer 3 · edited May 23 '17 at 12:10

1

Have a look at LINQ Select Distinct with Anonymous Types

I'm guessing r.ID is varying between the two products that are the same, but you have the same Products_Id?

edited May 23 '17 at 12:10

Community

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answered May 07 '12 at 03:48

Keith Nicholas

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Distinct elements in LINQ

3 Answers3

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