using System;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
using System.Collections;
比如：
// 打开数据库

转自：动态网制作指南 www.knowsky.com
public static SqlConnection OpenConnection()
  {
   SqlConnection mysqlConn = new SqlConnection(ConfigurationSettings.AppSettings["connstring"]);
  

   try
   {
    mysqlConn.Open();
   }
   catch (Exception e)
   {
    //rethrow this exception
    throw e;
   }

   return mysqlConn;
  }

// 执行SQL返回DataSet
public static DataSet GetDataSet(string SQLQuery)
  {
   SqlConnection cn = DBObject.OpenConnection();
   SqlDataAdapter da = new SqlDataAdapter(SQLQuery, cn);
   DataSet ds = new DataSet();
  
   da.Fill(ds);
  
   //release resources
   da.Dispose();
   da = null;
   cn.Close();
   cn = null;

   return ds;
  }

// 执行SQL语句
public static void ExecuteUpdateQuery(string SQLQuery)
  {
   SqlConnection cn = DBObject.OpenConnection();
   SqlCommand cmd = new SqlCommand();

   cmd.CommandText = SQLQuery;
   cmd.CommandType = CommandType.Text;
   cmd.Connection = cn;
   cmd.ExecuteNonQuery();
  
   cn.Close();
   cn = null;
  }