数据库创建连接的单例子模式

 
public class MySqlDbDataAccess 
{
private static MySqlConnection _connection = null;
private static readonly object SynObject = new object();
private static string _DatabaseConnectionString = "";
public MySqlDbDataAccess()
{
_DatabaseConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["DBConfig"].ConnectionString;
///初始化构造 数据库连接对象
_connection = connectInstance;
}
public static MySqlConnection connectInstance
{
get 
{
if (_connection == null)
{
lock (SynObject)
{
_connection = new MySqlConnection(_DatabaseConnectionString);

if (_connection.State != ConnectionState.Open)
{
_connection.Open();
}
}
}
return _connection;
}
}

}