C# 4 and .NET 4

Using Database Connections ❘ 821
In case you forget the format of database connection strings (as many of us do now
and then), the following URL is very handy: www.connectionstrings.com.
The example opens a database connection using the defi ned connection string and then closes that
connection. Once the connection has been opened, you can issue commands against the data source, and
when you are fi nished, the connection can be closed.
SQL Server has another mode of authentication — it can use Windows - integrated security, so that the
credentials supplied at logon are passed to SQL Server. This is accomplished by removing the uid and pwd
portions of the connection string, and adding in Integrated Security=SSPI .
In the download code available for this chapter, you will fi nd the fi le login.cs , which simplifi es the
examples in this chapter. It is linked to all the sample code and includes database connection information
used for the examples; you can alter this to supply your own server name, user, and password as
appropriate. This, by default, uses Windows - integrated security; however, you can change the username and
password as appropriate.
managing Connection strings
In the initial release of .NET, it was up to the developer to manage the database connection strings, which
was often done by storing a connection string in the application confi guration fi le or, more commonly, hard -
coded somewhere within the application itself.
Beginning with .NET 2.0, you have a predefi ned way to store connection strings, and even use database
connections in a type - agnostic manner — for example, it is now possible to write an application and then
plug in various database providers, all without altering the main application.
To defi ne a database connection string, you should use the section of the
confi guration fi le. Here, you can specify a name for the connection and the actual database connection
string parameters; in addition, you can also specify the provider for this connection type. Here is an
example:
< configuration >
...
< connectionStrings >
< add name="Northwind"
providerName="System.Data.SqlClient"
connectionString="server=(local);integrated security=SSPI;database=Northwind" / >
< /connectionStrings >
< /configuration >
You use this same connection string in the other examples in this chapter.
code download Connection String Example.txt
Once the database connection information has been defi ned within the confi guration fi le, you then need
to utilize this within the application. You will most likely want to create a method such as the following to
retrieve a database connection based on the name of the connection:
private DbConnection GetDatabaseConnection ( string name )
{
ConnectionStringSettings settings =
ConfigurationManager.ConnectionStrings[name];
DbProviderFactory factory = DbProviderFactories.GetFactory
( settings.ProviderName );
www.it-ebooks.info