C# 4 and .NET 4

Querying the Database ❘ OC273
foreach (Product item in query)
{
Console.WriteLine(item.ProductID + " | " + item.ProductName);
}
}
}
}
Console.ReadLine();
code download ConsoleApplication1.sln
In this case, a query object (again, a Table object) is populated with the query value of from
p in dc.Products select p;. This command, though shown on two lines for readability purposes, can
also be presented on a single line if you wish.
query expressions in detail
You will find that there are a number of query expressions that you can use from your code. The previous
example is a simple select statement that returns the entire table. The following list of items are some of the
other query expressions that you have at your disposal.
segmenTaTion
Project
Filter
Test
Join
Group
Aggregate
Partition
Set
Order
xynTaX
select
where , distinct
any(), all()
join on equals
group by , into , group join on
equals into
count([]), sum(), min(), max(),
avg()
skip [while] , take [while]
union, intersect, except
order by , [ascending | descending]
filtering using expressions
In addition to straight queries for the entire table, you can filter items using the where and distinct
options. The following provides an example of querying the Products table for a specific type of record:
var query = from p in dc.Products
where p.ProductName.StartsWith("L")
select p;
In this case, this query is selecting all the records from the Products table that start with the letter L. This
is done via the where p.ProductName.StartsWith(“L”) expression. You will find a large selection of
methods available from the ProductName property that allows you to fine-tune the filtering you need. This
operation produces the following results:
65 | Louisiana Fiery Hot Pepper Sauce
66 | Louisiana Hot Spiced Okra
67 | Laughing Lumberjack Lager
74 | Longlife Tofu
76 | Lakkalikööri
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