ADO.NET Name Spaces
Before you can use ADO.NET components , the appropriate name spaces must be included. The System.Data name space always needs to be included because this contains the core database components. Next, one of two name spaces must be included, depending on the source of your data. For a direct SQL Server connection, the System.Data.SqlClient name space should be used for best performance. For all other connection types, such as Access and Oracle, the System.Data.OleDb name space is required.