Represents an open connection to a data source.
Assembly: System.Data (in System.Data.dll)
An object represents a unique connection to a data source created by using a connection string or ODBC data source name (DSN). With a client/server database system, it is equivalent to a network connection to the server. Depending on the functionality supported by the native ODBC driver, some methods or properties of an object may not be available.
The object uses native resources such as ODBC environment and connection handles. You should always explicitly close any open objects by calling Close or Dispose before the object goes out of scope, or by placing the connection within a Using statement. Not doing this leaves the freeing of these native resources to garbage collection. It might not free them immediately. This, in turn, can eventually cause the underlying driver to run out of resources or reach a maximum limit. This has resulted in intermittent failures. For example, you might experience Maximum Connections -related errors while many connections are waiting to be deleted by the garbage collector. Explicitly closing the connections allows for a more efficient use of native resources, enhancing scalability and improving overall application performance.
To deploy high-performance applications, you frequently must use connection pooling. However, when you use the .NET Framework Data Provider for ODBC, you do not have to enable connection pooling because the provider manages this automatically.
If one of the Execute methods of the OdbcCommand class causes a fatal OdbcException (for example, a SQL Server severity level of 20 or greater), the may close. However, the user can reopen the connection and continue.
An application that creates an instance of the object can require all direct and indirect callers to have sufficient permission to the code by setting declarative or imperative security demands. creates security demands by using the OdbcPermission object. Users can verify that their code has sufficient permissions by using the OdbcPermissionAttribute object. Users and administrators can also use the Code Access Security Policy Tool (Caspol.exe) to modify security policy at the computer, user, and enterprise levels. For more information, see Code Access Security and ADO.NET.
For more information about handling warning and informational messages from the data source, see Connection Events (ADO.NET).
The following example creates an OdbcCommand and an . The is opened and set as the Connection property. The example then calls ExecuteNonQuery, and closes the connection. To accomplish this, the ExecuteNonQuery is passed a connection string and a query string that is an SQL INSERT statement.
Private Sub InsertRow(ByVal connectionString As String) Dim queryString As String = _ "INSERT INTO Customers (CustomerID, CompanyName) Values('NWIND', 'Northwind Traders')" Dim command As New OdbcCommand(queryString) Using connection As New OdbcConnection(connectionString) command.Connection = connection connection.Open() command.ExecuteNonQuery() ' The connection is automatically closed at ' the end of the Using block. End Using End Sub
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.