A brief description of the three core objects of ADO. net

SqlConnection // connection string

SqlCommand // the object for executing SQL commands

SqlDataReader // read records from the database

Note that you must disable DataReader even if you disable SqlConnection. Otherwise, an error will occur when you use unclosed DataReader next time.

The sample code is as follows:

Demo
Class Program
{

/// <Summary>
/// Application entry
/// </Summary>
/// <Param name = "args"> </param>
/// <Returns> </returns>
Static void Main (string [] args)
{
String connectionString = GetConnectString ();
String queryString = "select * from person where id = 2 ";
// String queryString = "delete from person where id = 2 ;";
Using (SqlConnection connection = new SqlConnection (connectionString ))
{
SqlCommand command = connection. CreateCommand ();
Command. CommandText = queryString;
Command. CommandType = CommandType. Text;

Try
{
Connection. Open ();
// Command. ExecuteNonQuery (); // execute a non-query command
SqlDataReader reader = command. ExecuteReader () // read data command;
While (reader. Read ())
{
For (int I = 0; I <reader. FieldCount; I ++)
{
Console. Write ("{0} \ t", reader [I]);
}
Console. writeline ();
}
Reader. Close ();
}
Catch (System. Exception ex)
{
Console. WriteLine (ex. Message );
}
}
Console. Read ();
}

/// <Summary>
/// Connection string
/// </Summary>
/// <Returns> </returns>
Public static string getconnectstring ()
{
Return "Data Source = (local); init ial catalog = mytestdb ;"
+ "Integrated Security = sspi ";
}