LINQ to Typed DataSet

Database -> DataSet -> Typed DataSet -> ADO.NET Entity Framework -> LINQ.

Add a typed dataset by Main Menu -> Data -> Add Data Source.

     using  NorthwindDataSetTableAdapters;

    NorthwindDataSet ds  =   new  NorthwindDataSet();
    TableAdapterManager adapters  =   new  TableAdapterManager();

    adapters.CustomersTableAdapter  =   new  CustomersTableAdapter();
    adapters.OrdersTableAdapter  =   new  OrdersTableAdapter();
    adapters.Order_DetailsTableAdapter  =   new  Order_DetailsTableAdapter();
    adapters.ProductsTableAdapter  =   new  ProductsTableAdapter();

    adapters.CustomersTableAdapter.Fill(ds.Customers);
    adapters.OrdersTableAdapter.Fill(ds.Orders);
    adapters.Order_DetailsTableAdapter.Fill(ds.Order_Details);
    adapters.ProductsTableAdapter.Fill(ds.Products);

     // Direct       
    Console.WriteLine( " Direct------------------------------------------- " );
     foreach  (var row  in  ds.Customers)
         if  (row.Country  ==   " USA " )
            Console.WriteLine( new  { row.CustomerID, row.Country, row.ContactName });

     // LINQ to Object
    var query  =  ds.Customers
        .Where(c  =>  c.Country  ==   " USA " )
        .Select(c  =>   new  { c.CustomerID, c.Country, c.ContactName });

    Console.WriteLine();
    Console.WriteLine( " LINQ to Object------------------------------------ " );
     foreach  (var row  in  query)
        Console.WriteLine(row);

     // LINQ to DataSet
    DataTable customersTable  =  (DataTable)ds.Customers;
    var query2  =
        from c  in  customersTable.AsEnumerable()
        where c.Field < string > ( " Country " )  ==   " USA "
        select c;

    Console.WriteLine();
    Console.WriteLine( " LINQ to DataSet------------------------------------ " );
     foreach  (var row  in  query2)
        Console.WriteLine( new
        {
            CustomerID  =  row.Field < string > ( " CustomerID " ),
            Country  =  row.Field < string > ( " Country " ),
            ContactName  =  row.Field < string > ( " ContactName " )
        });

If you create the typed DataSet with Visual Studio, your typed DataTable classes will be derived from the TypedTableBase<T> class, which implements the IEnumerable<T> interface. For this reason, it is not required to call AsEnumerable to get a wrapper. 

    var query2  =
         // from c in customersTable.AsEnumerable()
        from c  in  ds.Customers
        where c.Field < string > ( " Country " )  ==   " USA "
        select c;

 

Reference

---

MSDN: LINQ to DataSet
http://msdn.microsoft.com/en-us/library/bb386977.aspx