Select Distinct with AddRange in Entity Framework

Question

User2012297617 posted

I got this single line of code: viewModel.MyOrders.AddRange(responseModel.Data.Select(orders => orders));

I receive all the orders. If there are more than one row for the same order, I'd like to select the first one.  That way I don't get something like this:

Orders:
1111     UT
2222     VA
2222      FL
3333     CA

Instead, I need to get something like this:
1111   UT
2222   VA
3333   CA

Answer 1

User-2054057000 posted

You need to apply the group by clause https://docs.microsoft.com/en-us/dotnet/csharp/linq/group-query-results

Answer 2

User1120430333 posted
IMO, the only thing you can do is run a Distinct on the collection of orders to make a new collection of orders.

Answer 3

User2012297617 posted

I tried this, but do I need to add the name of the order field?

viewModel.MyOrders.AddRange(responseModel.Data.Select(orders => orders).Distinct());

How the query will identify that I need distinct order number, even if I have different States within the data?

Answer 4

User475983607 posted

One more column is required either an identity or sort.  Otherwise, 2222 can be VA or FL.

Answer 5

User2012297617 posted

right, which is good.   How do you recommend fixing this?

viewModel.MyOrders.AddRange(responseModel.Data.Select(orders => orders).Distinct());

Answer 6

User-474980206 posted

if you group by orderid (or whatever the key is), then you will get a grip for each order and in this group you will get a collection of the dups. you then need to summarize this collection to one row, say using first(), or summations.

var orders = response.Model.Data.GroupBy
(
    r => r.OrderIdId, 
    r => r,
    (key, g) => g.First()
);

Answer 7

User2012297617 posted

Thanks for your help!

Answer 8

User1120430333 posted
You would have to use a lambda expression on the Distinct.

https://www.elevenwinds.com/blog/linq-distinctby-with-lambda-expression-parameter/