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WCF 4.5 Multi-Layer Services Development with Entity Framework by Mike Liu

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Joining two tables

Although an association is a kind of join in LINQ, we can also explicitly join two tables using the Join keyword, as shown in the following code snippet:

    static void TestJoin()
    {
        using(NorthwindEntities NWEntities = new NorthwindEntities())
       {
        var categoryProducts =
            from c in NWEntities.Categories
            join p in NWEntities.Products 
            on c.CategoryID equals p.CategoryID 
            into productsByCategory
            select new {
                c.CategoryName,
                productCount = productsByCategory.Count()
            };
            
        foreach (var cp in categoryProducts)
        {
          Console.WriteLine("There are {0} products in category {1}",
                cp.productCount, cp.CategoryName);
        }
       }
    }

This is not so useful in the previous example because the Products and Categories tables are associated with a foreign key relationship. ...

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