Select all distinct values of variable in object array using lambda expression

user_9661426 0
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I have an array of objects with the property of ProductId. I would like to use a lambda expression to select all the distinct values of ProductId that are within my object array products.

Here I get the products

var products = Database.SqlQuery<StructuredProduct>("query").ToArray();

And I can group by distinct values of ProductId, but it still returns an array of objects, rather than an array of ProductIds

var productIds= products.GroupBy(p => p.ProductId).Select(group => group.First()).ToArray();

Any idea on how to use a Lambda Expression on the products array to get all distinct values of ProductIds?

lambda c#
3 Answers
var productIds= products.Select(p => p.ProductId).Distict();

But it may be even better to do this directly on the database, as part of the "query" sql command.

Joel_Coehoorn_30430

With LINQ method .Distinct()

var productIds = products.Select(p => p.ProductId).Distinct();
user_14018860

I've only ever done GroupBy operations with the query comprehension syntax. If you do that, group / by / into, the thing you group into has a property named key. That would contain your 'productid`

var results = from product in products
    group product by ProductId
    into individualProducts
    select individualProducts;

var productsArray = individualProducts.Select(p => p.Key).ToArray();

The items individualProducts collection each have a Key and a collection of things that have the same productid.

If you do this directly out of the database, all your operations will get nicely combined into a single SQL statement that will get executed when your code gets to .ToArray()

user_47394880
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