ADO.NET复习总结（6）-断开式数据操作

一、基础知识

主要类及成员（和数据库无关的）
（1）类DataSet：数据集，对应着库，属性Tables表示所有的表
（2）类DataTable：数据表，对应着表，属性Rows表示所有的行
（3）类DataRow：行数据，一个行数组，就对应着一个实体对象
         -》使用DataAdapter的Fill方法，可以将数据填充到DataSet或DataTable中

二、练习：完成学生表的crud

（1）dataGridView的填充：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;
using t2_StudentInfo;

namespace studentInfo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }   
        private void Form1_Load(object sender, EventArgs e)
        {
            string sql = "select * from studentinfo";
            using (SqlConnection conn = new SqlConnection("server=.;database=dbtest;uid=sa;pwd=123")) 
            {
                SqlDataAdapter sda = new SqlDataAdapter(sql,conn);
                DataTable table = new DataTable();
                sda.Fill(table);
                dataGridView1.DataSource = table;
            }
        }
    }
}

（2）重新封装SQLhelper

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace t2_StudentInfo
{
    public static partial class SqlHelper
    {
        private static string connStr = ConfigurationManager.ConnectionStrings["dbtest"].ConnectionString;

        public static int ExecuteNonQuery(string sql,params SqlParameter[] ps)
        {
            using (SqlConnection conn=new SqlConnection(connStr))
            {
                SqlCommand cmd=new SqlCommand(sql,conn);
                cmd.Parameters.AddRange(ps);
                
                conn.Open();
                return cmd.ExecuteNonQuery();
            }
        }

        public static object ExecuteScalar(string sql, params SqlParameter[] ps)
        {
            using (SqlConnection conn=new SqlConnection(connStr))
            {
                SqlCommand cmd=new SqlCommand(sql,conn);
                cmd.Parameters.AddRange(ps);

                conn.Open();
                return cmd.ExecuteScalar();
            }
        }

        public static DataTable ExecuteTable(string sql,params SqlParameter[] ps)
        {
            using (SqlConnection conn=new SqlConnection(connStr))
            {
                SqlDataAdapter adapter=new SqlDataAdapter(sql,conn);
                //用于进行select操作，可以通过SelectCommand属性获取此操作的SqlCommand对象
                adapter.SelectCommand.Parameters.AddRange(ps);

                DataTable dt=new DataTable();
                adapter.Fill(dt);

                return dt;
            }
        }

        public static SqlDataReader ExecuteReader(string sql,params SqlParameter[] ps)
        {
            SqlConnection conn=new SqlConnection(connStr);
            SqlCommand cmd=new SqlCommand(sql,conn);
            cmd.Parameters.AddRange(ps);

            conn.Open();

            return cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }
    }
}

（3）查询

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;
using t2_StudentInfo;

namespace studentInfo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            
            //连接查询
            string sql = "select * from StudentInfo inner join ClassInfo on StudentInfo.cid=ClassInfo.cId ";
            DataTable dt = SqlHelper.ExecuteTable(sql);
            dataGridView1.AutoGenerateColumns = false;
            dataGridView1.DataSource = dt;   
     
        }
      
        private void dataGridView1_CellFormatting_1(object sender, DataGridViewCellFormattingEventArgs e)
        {
            if (e.ColumnIndex == 2)
            {
                if (Convert.ToBoolean(e.Value))
                {
                    e.Value = "男";
                }
                else
                {
                    e.Value = "女";
                }
            }
        }
        
    }
}

（4）

A:列表：

B:列表代码：

private void FormAdd_Load(object sender, EventArgs e)
        {
            string sql = "select * from classinfo";
            DataTable dt = SqlHelper.ExecuteTable(sql);
            cdoClassInfo.DisplayMember = "CTitle";
            cdoClassInfo.ValueMember = "CId";
            cdoClassInfo.DataSource = dt;
        }

C:添加、

 private void button1_Click(object sender, EventArgs e)
        {
            string sql ="";
            if (string.IsNullOrEmpty(label1.Text))
            {
                //添加
                sql = "insert into studentinfo(sname,sgender,sbirthday,cid) values(@name,@gender,@birthday,@cid)";
            }
            else
            {
                //修改
                sql = "update studentinfo set sname=@name,sgender=@gender,sbirthday=@birthday,cid=@cid where sid=" +label1.Text;
            }

            SqlParameter[] ps =
            {
                new SqlParameter("@name",textBox1.Text), 
                new SqlParameter("@gender",radioButton1.Checked), 
                new SqlParameter("@birthday",dtpBirthday.Value), 
                new SqlParameter("@cid",cboClassInfo.SelectedValue), 
            };
            int result=SqlHelper.ExecuteNonQuery(sql, ps);
            if (result > 0)
            {
                FreshForm();
                this.Close();
            }
            else
            {
                MessageBox.Show("保存失败");
            }
        }

D:删除：

 private void removeToolStripMenuItem_Click(object sender, EventArgs e)
        {
            DialogResult result = MessageBox.Show("确定要删除吗？", "提示", MessageBoxButtons.OKCancel);
            if (result == DialogResult.Cancel)
            {
                return;
            }
            int sid = Convert.ToInt32(dataGridView1.SelectedRows[0].Cells[0].Value);
            string sql = "update studentinfo set isdelete=1 where sid=" + sid;
            if (SqlHelper.ExecuteNonQuery(sql) > 0)
            {
                LoadList();
            }
            else
            {
                MessageBox.Show("删除失败");
            }
        }

E:修改：

private void editToolStripMenuItem_Click(object sender, EventArgs e)
        {
            int id = Convert.ToInt32(dataGridView1.SelectedRows[0].Cells[0].Value);

            FormAdd formAdd=new FormAdd();
            formAdd.FreshForm += LoadList;
            ShowStudent += formAdd.ShowInfo;
            formAdd.Show();

            ShowStudent(id);//发布显示内容的消息
        }

-》事件（广播、消息）的代码实现：
《1》定义委托
《2》在发布消息的类型中定义事件
《3》在接收消息的类型中为事件添加方法