连接SQL数据库方法：

一、建立连接
    
    1、（使用System.Data.SqlClient）

<1>  string strcon;         //声明连接字串
            strcon = "server='(local)';database='mytable';uid='sa';pwd='sa';";   //编写连接字串
            SqlConnection con = new SqlConnection(strcon);     //新建SQL连接  默认构造函数
            try
            {
                con.Open();         //打开SQL连接
                Label1.Text = "连接数据库成功";       //提示成功信息
            }
            catch
            {
                Label1.Text = "无法连接数据库";              //提示失败信息
            }

<2>  SqlConnection con = new SqlConnection();      //创建连接对象
            con.ConnectionString = "server='(local)';database='mytable';uid='sa';pwd='sa'";     //设置连接字串
            try
            {
                con.Open();         //尝试打开连接
                Label1.Text = "连接成功";       //提示打开成功
                con.Close();         //关闭连接
            }
            catch
            {
                Label1.Text = "连接失败";       //提示打开失败
            }
         
     2、（使用System.Data.OleDb）
       
        <1> string str =
            "Provider=SQLOLEDB;Data Source=(local);Initial Catalog=mytable;uid=sa;pwd=sa";
            OleDbConnection con = new OleDbConnection(str);
            try
            {
                con.Open();                //尝试打开连接
                Label1.Text = "连接成功";       //提示连接成功
                con.Close();         //关闭连接
            }
            catch
            {
                Label1.Text = "连接失败";       //提示连接失败
            }

<2> OleDbConnection con= new OleDbConnection();             //创建连接对象
            con.ConnectionString="Provider=SQLOLEDB;Data
            Source=(local);Initial Catalog=mytable;uid=sa;pwd=sa";           //初始化连接字串
            try
            {
                con.Open();                //尝试打开连接
                Label1.Text = "连接成功";       //提示连接成功
                con.Close();         //关闭连接
            }
            catch
            {
                Label1.Text = "连接失败";       //提示连接失败
            }

注：命名空间必须加上using System.Data.SqlClient或using System.Data.OleDb

二、填充Dataset数据集

SqlDataAdapter da=new SqlDataAdapter("select * from news",con);   //创建适配器
            DataSet ds = new DataSet();        //创建数据集
            da.Fill(ds, "tablename");        //Fill方法填充

三、显示Dataset
         
             ds.Tables["tablename"].Rows[0]["title"].ToString();    //获取数据集
            
              for (int i = 0; i < ds.Tables["tablename"].Rows.Count; i++)   //遍历DataSet数据集
            {
                Response.Write(ds.Tables["tablename"].Rows[i]["title"].ToString()+"<br/>");
            }

DataList1.DataSource = ds;        //绑定数据集
            DataList1.DataMember = "tablename";
            DataList1.DataBind();        //绑定数据

插入或删除操作：

string str = "server='(local)';database='mytable';uid='sa';pwd='sa'";  //创建数据库连接字串
            SqlConnection con = new SqlConnection(str);
            con.Open();          //打开数据库连接
            SqlCommand cmd = new SqlCommand("insert into news values ('title')",con);           //建立Command对象
            cmd.ExecuteNonQuery();        //执行SQL语句

连接ACCESS数据库：

（使用System.Data.OleDb）

string str = "provider=Microsoft.Jet.OLEDB.4.0 ;Data Source="
            + Server.MapPath("access.mdb") + "";      //使用相对路径
            OleDbConnection con = new OleDbConnection(str);     //构造连接对象
            try
            {
                con.Open();         //打开连接
                Label1.Text = "连接成功";       //提示连接成功
                con.Close();
            }
            catch(Exception ee)         //抛出异常
            {
                Label1.Text = "连接失败";
            }