C# 4 and .NET 4

object Query ❘ 877
The following sections of this book make use of a Formula1 database where you can see the entities created
from the designer in Figure 31-7.
figure 31-7
Queries can be defined with the ObjectQuery class, or the class that derives from it: ObjectSet.
Let’s start with a simple query to access all Racer entities. The Racers property of the generated
Formula1Entities class returns a ObjectSet:
using (Formula1Entities data = new Formula1Entities(connection))
{
ObjectSet racers = data.Racers;
Console.WriteLine(racers.CommandText);
Console.WriteLine(racers.ToTraceString());
}
The Entity SQL statement that is returned from the CommandText property is shown here:
[Formula1Entities].[Racers]
code snippet Formula1Demo/Program.cs
And this is the generated SELECT statement to retrieve the records from the database that is shown by the
ToTraceString() method:
SELECT
[Extent1].[Id] AS [Id],
[Extent1].[Firstname] AS [Firstname],
[Extent1].[Lastname] AS [Lastname],
[Extent1].[Country] AS [Country],
[Extent1].[Starts] AS [Starts],
[Extent1].[Wins] AS [Wins]
FROM [dbo].[Racers] AS [Extent1]
Instead of accessing the Racers property from the object context, you can also create a query with the
CreateQuery() method:
ObjectQuery racers = data.CreateQuery("[Formula1Entities].[Racers]");
This is similar to using the Racers property.
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