How to retrieve a subset of rows from subquery using LINQ

 I have spent hours to get the LINQ query on how to retrieve a subset of rows from subquery using LINQ.

How I mean is not a single return like this:

var queryGroupMax =

        from student in students

        group student by student.Year into studentGroup

        select new

        {

            Level = studentGroup.Key,

            HighestScore =

            (from student2 in studentGroup

             select student2.ExamScores.Average()).Max()

        };

The subquery about only return a single Max() value.

What I mean by subquery is those that returns many rows, like:

SELECT * FROM  [Products] WHERE [ProductID] IN (SELECT ProductID FROM [dbo].[Order Details])

Like the subquery above SELECT ProductID FROM [dbo].[Order Details] returns all the ProductID from the Order Detail Table.

I never found any correct example out there. I downloaded Linqer, somehow the Linqer giving me the almost correct answer.

var result = from Products in db.Products where (from Order_Details in db.Order_Details
select new{Order_Details.ProductID}).Contains(new { ProductID = ()Products.ProductID })
select new {  Products.ProductID,
Products.ProductName,
Products.SupplierID,
Products.CategoryID,
Products.QuantityPerUnit,
Products.UnitPrice,
Products.UnitsInStock,
Products.UnitsOnOrder,
Products.ReorderLevel,
Products.Discontinued
};

I somehow managed to sweat it through to modify if without the (). Tested and it works.

var result = from Products in db.Products where (from Order_Details in db.Order_Details
select new{Order_Details.ProductID}).Contains(new { ProductID = Products.ProductID })
select new {  Products.ProductID,
Products.ProductName,
Products.SupplierID,
Products.CategoryID,
Products.QuantityPerUnit,
Products.UnitPrice,
Products.UnitsInStock,
Products.UnitsOnOrder,
Products.ReorderLevel,
Products.Discontinued
};

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About chanmingman

Since March 2011 Microsoft Live Spaces migrated to Wordpress (http://www.pcworld.com/article/206455/Microsoft_Live_Spaces_Moves_to_WordPress_An_FAQ.html) till now, I have is over 1 million viewers. This blog is about more than 50% telling you how to resolve error messages, especial for Microsoft products. The blog also has a lot of guidance teaching you how to get stated certain Microsoft technologies. The blog also uses as a help to keep my memory. The blog is never meant to give people consulting services or silver bullet solutions. It is a contribution to the community. Thanks for your support over the years. Ming Man is Microsoft MVP since year 2006. He is a software development manager for a multinational company. With 25 years of experience in the IT field, he has developed system using Clipper, COBOL, VB5, VB6, VB.NET, Java and C #. He has been using Visual Studio (.NET) since the Beta back in year 2000. He and the team have developed many projects using .NET platform such as SCM, and HR based applications. He is familiar with the N-Tier design of business application and is also an expert with database experience in MS SQL, Oracle and AS 400.
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