C# 4 and .NET 4

entity Client ❘ 867
EntityDataReader reader = command.ExecuteReader(
CommandBehavior.CloseConnection | CommandBehavior.SequentialAccess);
while (reader.Read())
{
Console.WriteLine("{0}, {1}", reader["Title"], reader["Publisher"]);
}
reader.Close();
code snippet BooksDemo/Program.cs
The code is done in the same way as in Chapter 30. The only real difference is the connection string and the
Entity SQL statements; that ’ s why we look at these now.
Connection string
With the earlier code snippet, the connection string is read from the confi guration fi le. The connection
string is required for EDM and is different from the normal ADO.NET connection string because mapping
information is required. The mapping is defi ned with the keyword metadata . metadata requires three
things: a delimited list of mapping fi les, Provider for the invariant provider name to access the data source,
and a Provider connection string to assign the provider - dependent connection string.
The delimited list of mapping fi les references the fi les BooksModel.csdl , BooksModel.ssdl , and
BooksModel.msl , which are contained within resources in the assembly as defi ned with the res: prefi x.
Within Visual Studio, the designer uses just one fi le, BooksModel.edmx , which contains CSDL, SSDL,
and MSL. Setting the property Custom Tool to EntityModelCodeGenerator creates three fi les that are
contained within resources.
Within the connectionString setting you can fi nd the connection string to the database with the
connection string setting. This part is the same as a simple ADO.NET connection string and depends on the
provider that is set with the provider setting:
With the connection string you can also specify CSDL, SSDL, and MSL fi les that are
not contained as a resource in the assembly. This is useful if you want to change the
content of these fi les after deployment of the project.
entity sql
For querying data with the Entity Client, Entity SQL is used. Entity SQL enhances T - SQL by adding types.
This syntax doesn ’ t require joins because associations of entities can be used instead.
Here, just a few syntax options are shown that help you start with Entity SQL. In the MSDN
documentation you can fi nd the complete reference.
The previous example showed how Entity SQL uses defi nitions from the CSDL in the EntityContainer
and EntitySet — for example, BooksEntities.Books to get all the books from the table Books because
the Books EntitySet maps to the Books EntitySet in the SSDL.
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