asp.net中怎么判断数据库连接未关闭呢？

asp.net中怎么判断数据库连接未关闭呢？

if(conn.State != System.Data.ConnectionState.Closed && conn != null)
{
//连接未关闭，conn是数据库连接的Connection

}

if(conn.Connected) { 连接未关闭 }

数据库连接类 sqlhelper private static string connectionstring="data source=.;initial catalog=hlrz;user id=sa;pwd=21";     public static sqlconnection connection = new sqlconnection(connectionstring); 数据查询类： public list<hlcontent> selecttitleandcontent(int content_typeid)     {     string sql = "select * from hlcontent where content_typeid='" + content_typeid + "'";     list<hlcontent> list = new list<hlcontent>();     try     {     sqlcommand comm = new sqlcommand(sql, sqlhelper.connection);     sqlhelper.connection.open();     sqldatareader dr = comm.executereader();     while (dr.read())     {     hlcontent content = new hlcontent();     if (dr["content_content"].tostring().length > 20)     {     content.content_content = dr["content_content"].tostring().substring(0, 20);     }     else     {     content.content_content = dr["content_content"].tostring();     }     content.content_name = dr["content_name"].tostring();     content.contentid = (int)dr["contentid"];     list.add(content);     }     dr.close();     return list;     }     catch (exception)     {     throw;     }     finally     {     sqlhelper.connection.close();     }     }

判断Connecton