asp.net 连接数据库的问题

我在web.config里写了这个代码



//HAN-PC\SQLEXPRESS 是我的服务器名称，sql Server的
//uid是han-PC\han 没密码

然后在app code
public static string connstring = ConfigurationManager.AppSettings["cn"];
SqlDataAdapter dap = new SqlDataAdapter(sql, connstring);
但是好像连不到数据库，怎么回事，求指教，本人菜鸟一只

出错么？ 把错误信息发出来

给你一个dbhelper、    public static class dbhelper     {     private static sqlconnection connection = null;     /// <summary>     /// 得到数据库连接     /// </summary>     public static sqlconnection connection     {     get     {     string connetionstring = configurationmanager.connectionstrings["myconnectionstring"].connectionstring;//这里的连接字符串写在配置文件里、     if (connection == null)     {     connection = new sqlconnection(connetionstring);     connection.open();     }     else if (connection.state == connectionstate.closed)     {     connection = new sqlconnection(connetionstring);     connection.open();     }     else if (connection.state == connectionstate.broken)     {     connection.close();     connection.open();     }     return connection;     }     }     /// <summary>     /// 增、删、改、操作     /// </summary>     /// <param name="sqlstr">sql语句</param>     /// <param name="type">执行类型</param>     /// <param name="para">参数数组</param>     /// <returns>影响行数</returns>     public static int executecommand(string sqlstr, commandtype type, sqlparameter[] para)     {     try     {     using (sqlcommand cmd = new sqlcommand(sqlstr, connection))     {     cmd.commandtype = type;     if (para != null && para.length > 0)     cmd.parameters.addrange(para);     return cmd.executenonquery();     }     }     catch (sqlexception ex)     {     throw ex;     }     }     /// <summary>     /// 查询单条记录     /// </summary>     /// <param name="sqlstr">sql字符串</param>     /// <param name="type">执行类型</param>     /// <param name="para">参数数组</param>     /// <returns>单个object值</returns>     public static object getscalar(string sqlstr, commandtype type, sqlparameter[] para)     {     try     {     using (sqlcommand cmd = new sqlcommand(sqlstr, connection))     {     cmd.commandtype = type;     if (para != null && para.length > 0)     cmd.parameters.addrange(para);     return cmd.executescalar();     }     }     catch (sqlexception ex)     {     throw ex;     }     }     /// <summary>     /// 查询多条记录     /// </summary>     /// <param name="sqlstr">sql字符串</param>     /// <param name="type">执行类型</param>     /// <param name="para">参数数组</param>     /// <returns>sqldatareader对象</returns>     public static sqldatareader getreader(string sqlstr, commandtype type, sqlparameter[] para)     {     try     {     using (sqlcommand cmd = new sqlcommand(sqlstr, connection))     {     cmd.commandtype = type;     if (para != null && para.length > 0)     cmd.parameters.addrange(para);     return cmd.executereader();     }     }     catch (sqlexception ex)     {     throw ex;     }     }     /// <summary>     /// 查询多条记录     /// </summary>     /// <param name="sqlstr">sql字符串</param>     /// <param name="type">执行类型</param>     /// <param name="para">参数数组</param>     /// <returns>dataset对象</returns>     public static datatable getdataset(string sqlstr, commandtype type, sqlparameter[] para)     {     try     {     using (sqlcommand cmd = new sqlcommand(sqlstr, connection))     {     cmd.commandtype = type;     if (para != null && para.length > 0)     cmd.parameters.addrange(para);     dataset dataset = new dataset();     new sqldataadapter(cmd).fill(dataset);     return dataset.tables[0];     }     }     catch (sqlexception ex)     {     throw ex;     }     }     }

配置文件(web.config)

<add name="myconnectionstring" connectionstring="data source=.;initial catalog=dbname;integrated security=true" providername="system.data.sqlclient"/>

这里我的数据库用的是sql2005、密码为空、

祝你好运、、、

string strConn = ConfigurationManager.ConnectionStrings["cn"].ConnectionString; MySqlConnection cn = new MySqlConnection(cn); cn.Open();