连接数据库如何封装?
连接字符转已经写到web.config文件中

<?xml   version= "1.0 "   encoding= "utf-8 "?>
<configuration>
        <appSettings/>
        <connectionStrings>
                <add   name= "ConnectionString "   connectionString= "Data   Source=250;Persist   Security   Info=True;User   ID=chenyi;Password=123456;Unicode=True "
                        providerName= "System.Data.OracleClient "   />
        </connectionStrings>
        <system.web>
                  <compilation   debug= "false "   />
                    <authentication   mode= "Windows "   />
                        </system.web>
</configuration>

连接的类该怎么写?
在页面中怎么调用它来输出表数据,给个例子好吗!

------解决方案--------------------
//查看
public DataSet selnews()
{
string connString = System.Configuration.ConfigurationSettings.AppSettings[ "ConnectionString "];
SqlConnection con = new SqlConnection(connString);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = new SqlCommand( "select * from 你的表名 ",con);
DataSet ds = new DataSet();
da.Fill(ds);
return ds;
}
------解决方案--------------------
using System;
using System.Data;
using System.Data.SqlClient;
namespace DBAccess
{
/// <summary>
/// Class1 的摘要说明。
/// </summary>
public class DB
{
SqlConnection conn = new SqlConnection ( "server=(local);database=pubs;uid=sa;pwd=sa ");
SqlCommand cmd = new SqlCommand ();
public DB()
{
//
// TODO: 在此处添加构造函数逻辑
//
}

/// <summary>
/// 执行存储过程,返回DataSet
/// </summary>
/// <param name= "cmd "> 存储过程参数数组 </param>
/// <param name= "proc "> 存储过程名 </param>
/// <returns> DataSet </returns>
public DataSet returnDataSet(string proc,SqlParameter[] paras)
{
this.cmd.Connection = conn;
this.cmd.CommandType = CommandType.StoredProcedure;
this.cmd.CommandText = proc;
if(paras!=null && paras.Length > 0)
{
foreach(SqlParameter p in paras)
{
cmd.Parameters.Add(p);
}
}
SqlDataAdapter da = new SqlDataAdapter ();
DataSet ds = new DataSet ();
da.Fill(ds);

return ds;
}

/// <summary>
/// 执行sql语句
/// </summary>
/// <param name= "sql "> sql查询语句 </param>
/// <returns> </returns>
public DataSet returnDataSet(string sql)
{

SqlDataAdapter da = new SqlDataAdapter(sql,conn);
DataSet ds = new DataSet ();
da.Fill(ds);

return ds;
}

}
}