(Linq) how to find the rows from a manytomany with most up-to-date

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hi there,

I have a entity relationship data table: vendor(1)--> inventory(many)<-- product(1), and I try to find the VendorId("A0001")'s all products with the most up-to-date inventory records.

SQL Table:

C#

InvId	   createDate	              vendorId     productId
1	       2016-03-11 21:11:09.677	  A0001	       1
2	       2016-03-11 21:26:09.647	  A0002	       1
3	       2016-03-11 21:26:09.647	  A0001	       1
4	       2016-03-11 21:26:43.707	  A0001	       5
5	       2016-03-11 21:45:03.013	  A0001	       1
6	       2016-03-11 21:26:09.647	  A0003	       2

can anyone help me with the linq statement?

What I have tried:

var parents = joda.inventory.AsEnumerable().Where(row => row.vendorId == vendorId);

var childProdcut = joda.inventory.AsEnumerable().Where(row => parents.Any(p => p.productId == row.productId && row.moveOut != "Y")).OrderBy(row => row.productId).First();

The result has duplicated productIds.

Posted 14-Mar-16 6:39am

Pai809

Updated 14-Mar-16 14:03pm

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Sascha Lefèvre · Accepted Answer · 2016-03-14T14:03:00

I'm a bit irritated by the fact that you've shown a column moveOut in "What you have tried" but not in your table - but the following should at least give you an idea, if its not exactly what you want.

Key points: Grouping the rows by productId, then in each productId-group order the rows by their createDate so that the latest appears first, then taking the first one and getting the InvId of it:

C#

var results = joda.inventory.AsEnumerable()
    .Where(row => row.vendorId == vendorId)
    .GroupBy(row => row.productId)
    .Select(grp => new
    {
        productId = grp.Key,
        invId = grp.OrderByDescending(row => row.createDate).First().InvId
    });

The result results is an enumeration (or a List, if you append a .ToList() at the end) of an "anonymous type" which holds the productId and the invId. If you need help with dealing with an "anonymous type" please leave a comment.