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ADO.NET connections Connecting to SQL Server and Oracle ADO.NET connections 1 Objectives • The objectives of this slide show are – to show different connection strings using very simple examples • This slide show uses the connected architecture – no disconnected DataSets • All examples are simple console programs – no GUI, no ASP.NET – focus on the important aspect: connections ADO.NET connections 2 ADO.NET in brief • Connection object – created using a connection string – models a physical connection to the database • Command object – created using a connection object – models a SQL statement • Reader object – created using a command object – models the result of an SQL statement • select or the like ADO.NET connections 3 Connection strings • Connection string holds information on – data source (server) – database name – user name and password • The structure of the connection string depends on – the database – the ADO.NET package used • Further information – www.connectionstrings.com is a good source ADO.NET connections 4 Trusted connections • Some DBMS' can use the operating system username and password to connect to a database. • Most common in Microsoft technologies – Windows + SQL Server • … integrated security=SSPI; … ADO.NET connections 5 SQL Server connection • Package System.Data.SqlClient • Classes – SqlConnection – SqlCommand – SqlDataReader • Example – SqlServerTest.cs ADO.NET connections 6 Oracle connection • Package System.Data.OracleClient – in .NET framework 1.1 – must be activated during compile • csc /r:System.Data.OracleClient.dll filename.cs • example: compileOracle.bat • Classes – OracleConnection – OracleCommand – OracleDataReader • Example – OracleTest.cs ADO.NET connections 7 OLE DB connections • OLE – Object Linking and Embedding – General Microsoft component technology • OLE DB – General way of using databases in ADO.NET • Not specific to any DBMS – Tries to replace ODBC – Depending on the connection string a program can connect to any database using OLE DD – Examples • SqlServerOleDbTest.cs • OracleOleDbTest.cs ADO.NET connections 8 ADO.NET interfaces • The program can be made a bit more flexible (i.e. easier to change DBMS) using interfaces instead of classes • Package System.Data • Interfaces – IDbConnection – IDbCommand – IDataReader • The connection object must be created using a real class (i.e. not an interface) • Example – SqlServerTestInterface ADO.NET connections 9 Handling exceptions • A database connection is a scarce resource – a database connection must be closed (handed back to the connection pool) after use - not matter what if we have an exception or not • Code pattern SomeConnection con = null; try { con = new SomeConnection(…); use the connection } finally { if (con != null) { con.close; } } ADO.NET connections 10