以users表为例，有三个字段，自增长的编号id，int类型；名称name，nvarchar类型，密码pwd，nvarchar类型
首先在vs2005中引入using System.Data.SqlClient;命名空间
        /// <summary>
        /// 增加
        /// </summary>
        /// <param name="name">姓名</param>
        /// <param name="pwd">密码</param>
        /// <returns></returns>
        public int Insert(string name,string pwd)
        {
            SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=Test;Integrated Security=True");//Initial Catalog后面跟你数据库的名字,如果你的SqlServer服务器名称后面不带SQLEXPRESS，那么Data Source=.
            conn.Open();           
            string sql = "insert into users(name,pwd) values(@name,@pwd)";
            SqlCommand cmd = new SqlCommand(sql,conn);
            SqlParameter parn = new SqlParameter("@name",name);
            cmd.Parameters.Add(parn);
            SqlParameter parp = new SqlParameter("@pwd", pwd);
            cmd.Parameters.Add(parn);
            int result = cmd.ExecuteNonQuery();//result接收受影响行数，也就是说result大于0的话表示添加成功
            conn.Close();
            cmd.Dispose();
            return result;
        }

/// <summary>
        /// 删除
        /// </summary>
        /// <param name="name">姓名</param>
        /// <param name="pwd">密码</param>
        /// <returns></returns>
        public int Update(int id)
        {
            SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=Test;Integrated Security=True");//Initial Catalog后面跟你数据库的名字,如果你的SqlServer服务器名称后面不带SQLEXPRESS，那么Data Source=.
            conn.Open();
            string sql = "delete from users where id=@id";
            SqlCommand cmd = new SqlCommand(sql, conn);
            SqlParameter parn = new SqlParameter("@id", id);
            cmd.Parameters.Add(parn);       
            int result = cmd.ExecuteNonQuery();//result接收受影响行数，也就是说result大于0的话表示删除成功
            conn.Close();
            cmd.Dispose();
            return result;

}

/// <summary>
        /// 修改
        /// </summary>
        /// <param name="name">姓名</param>
        /// <param name="pwd">密码</param>
        /// <returns></returns>
        public int Insert(string name, string pwd,int id)
        {
            SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=Test;Integrated Security=True");//Initial Catalog后面跟你数据库的名字,如果你的SqlServer服务器名称后面不带SQLEXPRESS，那么Data Source=.
            conn.Open();           
            string sql = "update users set name=@name,pwd=@pwd where id=@id";
            SqlCommand cmd = new SqlCommand(sql, conn);
            SqlParameter parn = new SqlParameter("@name", name);
            cmd.Parameters.Add(parn);
            SqlParameter parp = new SqlParameter("@pwd", pwd);
            cmd.Parameters.Add(parn);
            SqlParameter pari = new SqlParameter("@id", id);
            cmd.Parameters.Add(pari);
            int result = cmd.ExecuteNonQuery();//result接收受影响行数，也就是说result大于0的话表示修改成功
            conn.Close();
            cmd.Dispose();
             return result;

}

/// <summary>
        /// 查询
        /// </summary>
        /// <returns></returns>
        public DataTable Select()
        {
            SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;Initial Catalog=Test;Integrated Security=True");//Initial Catalog后面跟你数据库的名字,如果你的SqlServer服务器名称后面不带SQLEXPRESS，那么Data Source=.
            conn.Open();           
            string sql = "select * from users";
            SqlCommand cmd = new SqlCommand(sql, conn);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            sda.Fill(dt);          
            conn.Close();
            cmd.Dispose();
            return dt;
        }
方法写好后，下面举一个查询的例子，在form窗体中拖一个DataGridView,然后在Load方法中
    private void Form1_Load(object sender, EventArgs e)
        {
              dataGridView1.DataSource = Select();
        }
这样一运行，DataGridView中就会显示数据了