本实例将通过c# winform实现简单的分页功能，需要的基础知识有SQL语句，c#语言基础以及c# winform的一些简单知识。
这是一个简单的分页查询的界面，可以输入任意字段进行查询，这四个字段在数据准备会提到，整体界面如图1所示。
图1
中间显示是一个DataGridView，编辑好列和id，SortMode选择Automatic，意思是所有列自动铺满DataGridView，如图2所示。
图2
本实例涉及到删查改，因此要有数据表以及对数据表进行操作的代码。数据库表非常简单，如图3所示，分别有对应四个字段。
图3
later_back模型类对应数据库操作类代码如下：
using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using WindowsFormsApp1.Bean;
namespace WindowsFormsApp1.SqlHelper
{
class LaterBackHelper
{
public LaterBackHelper(){}
public void insert(LaterBack laterBack)
{
string sql = "insert into later_back(dormitory_id,student_no,time,reason) values('" + laterBack.Dormitory_id + "','" + laterBack.Student_no + "'," + "'" + laterBack.Time + "',"
+ "'" + laterBack.Reason + "')";
try
{
int iRet = SqlHelperBase.ExecuteSql(sql);
if (iRet > 0)
{
MessageBox.Show("新增成功", "系统提示");
}
else
{
MessageBox.Show("新增失败", "系统提示");
}
}
catch (Exception)
{
throw;
}
}
public int update(LaterBack laterBack)
{
string sql = "update later_back set reason='" + laterBack.Reason + "' where student_no= '" + laterBack.Student_no + "' and"
+ " time = '" + laterBack.Time + "' and " + " dormitory_id= '" + laterBack.Dormitory_id + "'";
try
{
int iRet = SqlHelperBase.ExecuteSql(sql);//这里返回的是受影响的行数，为int值。可以根据返回的值进行判断是否插入成功。
if (iRet > 0)
{
MessageBox.Show("修改成功", "系统提示");
}
else
{
MessageBox.Show("修改失败", "系统提示");
}
return iRet;
}
catch (Exception)
{
throw;
}
}
public int delete(LaterBack laterBack)
{
string sql = "delete from later_back where dormitory_id='" + laterBack.Dormitory_id + "' and" + " student_no= '" + laterBack.Student_no + "' and"
+ " time = '" + laterBack.Time + "' and" + " reason= '" + laterBack.Reason+"'";
try
{
int iRet = SqlHelperBase.ExecuteSql(sql);//这里返回的是受影响的行数，为int值。可以根据返回的值进行判断是否插入成功。
if (iRet > 0)
{
MessageBox.Show("删除成功", "系统提示");
}
else
{
MessageBox.Show("删除失败", "系统提示");
}
return iRet;
}
catch (Exception)
{
throw;
}
}
public List<LaterBack> getAllLaterBacks()
{
List<LaterBack> laterBacks= new List<LaterBack>();
string sql = "select * from later_back";
MySqlDataReader mySqlDataReader = SqlHelperBase.ExecuteReader(sql);
while (mySqlDataReader.Read())
{
LaterBack laterBack = new LaterBack(int.Parse(mySqlDataReader[0].ToString()), int.Parse(mySqlDataReader[1].ToString()), mySqlDataReader[2].ToString(),
mySqlDataReader[3].ToString());
laterBacks.Add(laterBack);
}
mySqlDataReader.Close();
return laterBacks;
}
public List<LaterBack> getAllLaterBacks(int student_no)
{
List<LaterBack> laterBacks= new List<LaterBack>();
string sql = "select * from later_back where student_no ='" + student_no + "'";
MySqlDataReader mySqlDataReader = SqlHelperBase.ExecuteReader(sql);
while (mySqlDataReader.Read())
{
LaterBack laterBack = new LaterBack(int.Parse(mySqlDataReader[0].ToString()), int.Parse(mySqlDataReader[1].ToString()), mySqlDataReader[2].ToString(),
mySqlDataReader[3].ToString());
laterBacks.Add(laterBack);
}
mySqlDataReader.Close();
return laterBacks;
}
public DataSet getAllDataSet()
{
string sql = "select * from later_back";
return SqlHelperBase.GetDataSet(sql);
}
//模糊查询
public DataSet getDataSet(LaterBack laterBack)
{
string sql="";
if(laterBack.Student_no != -1)
{
if (laterBack.Dormitory_id != -1) sql = "select * from later_back where dormitory_id like '%" + laterBack.Dormitory_id
+ "%' and student_no like '%" + laterBack.Student_no + "%' and time like '%" + laterBack.Time
+ "%' and reason like '%" + laterBack.Reason + "%'";
else sql = "select * from later_back where student_no like '%" + laterBack.Student_no + "%' and time like '%" + laterBack.Time
+ "%' and reason like '%" + laterBack.Reason + "%'";
}
else
{
if (laterBack.Dormitory_id != -1) sql = "select * from later_back where dormitory_id like '%" + laterBack.Dormitory_id
+ "%' and time like '%" + laterBack.Time+ "%' and reason like '%" + laterBack.Reason + "%'";
else sql = "select * from later_back where time like '%" + laterBack.Time
+ "%' and reason like '%" + laterBack.Reason + "%'";
}
return SqlHelperBase.GetDataSet(sql);
}
}
}
实现分页时，我的思想是，在每次查询时得到一个dataset1，然后在分页时根据一个from_index和一个end_index去得到当前页面要显示的dataset2，用dataset2来刷新当前要显示的数据，然后在dataset2里头支持行数据的修改与删除，可能从这么写不大合适，但是能完成分页的功能，仅供参考。源码如下：
using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using WindowsFormsApp1.Bean;
using WindowsFormsApp1.CacheUtil;
using WindowsFormsApp1.SqlHelper;
namespace WindowsFormsApp1
{
public partial class StudentLateBackPanelRightSelect : Form
{
private LaterBackHelper laterBackHelper;
private string []page_counts = { "5","6","7","8","9","10","15","20"};
private int total_page, page_step, current_page_index, total_count;
private DataSet dataSet;
public StudentLateBackPanelRightSelect()
{
laterBackHelper = new LaterBackHelper();
dataSet = laterBackHelper.getAllDataSet();
total_count = dataSet.Tables[0].Rows.Count;
page_step = 5;
total_page = Convert.ToInt16(Math.Ceiling(Convert.ToDouble(total_count) / page_step));
InitializeComponent();
initView(GetViewDataSet(dataSet,1,5));
comboBox_page_count.Items.AddRange(page_counts);
comboBox_page_count.SelectedIndex = 0;
label_all_item_count.Text = total_count.ToString();
label_page_count.Text = total_page.ToString();
}
//每次点击时刷新全局数据
private void initDataPage(int total_count,int page_step, int current_page_index)
{
this.total_count = total_count;
this.page_step = page_step;
this.total_page = Convert.ToInt16(Math.Ceiling(Convert.ToDouble(total_count) / page_step));
this.current_page_index = current_page_index;
}
//初始化界面并加载数据
private void initView(DataSet ds)
{
dataGridView.AutoGenerateColumns = false;
dataGridView.DataSource = ds.Tables[0];
this.dataGridView.Columns["dor_id"].DataPropertyName = ds.Tables[0].Columns[0].ToString();
this.dataGridView.Columns["stu_id"].DataPropertyName = ds.Tables[0].Columns[1].ToString();
this.dataGridView.Columns["time"].DataPropertyName = ds.Tables[0].Columns[2].ToString();
this.dataGridView.Columns["reason"].DataPropertyName = ds.Tables[0].Columns[3].ToString();
}
private void button_select_Click(object sender, EventArgs e)
{
string stu_id = textBox_stu_id.Text, dor_id = textBox_dor_id.Text, time = textBox_time.Text, reason = textBox_reason.Text;
if(stu_id.Equals("")&& dor_id.Equals("") && time.Equals("") && reason.Equals(""))
{
return;
}
if (dor_id.Equals("")) dor_id = "-1";
if (stu_id.Equals("")) stu_id = "-1";
LaterBack laterBack = new LaterBack(int.Parse(dor_id), int.Parse(stu_id), time, reason);
dataSet.Clear();
dataSet = laterBackHelper.getDataSet(laterBack);
initDataPage(dataSet.Tables[0].Rows.Count, page_step, 1);
initView(GetViewDataSet(dataSet, 1, page_step));
label_page_count.Text = total_page.ToString();
label_page_range.Text = "1-" + page_step.ToString();
label_all_item_count.Text = total_count.ToString();
}
//只能输入数字
private void only_num_press(object sender, KeyPressEventArgs e)
{
if (!(Char.IsNumber(e.KeyChar)) && e.KeyChar != (char)8)
{
e.Handled = true;
}
}
//对行数据进行删除或修改操作
private void dataGridView_CellClick(object sender, DataGridViewCellEventArgs e)
{
string action = dataGridView.Columns[e.ColumnIndex].Name;//操作类型
var cells = dataGridView.Rows[e.RowIndex].Cells;
LaterBack laterBack = new LaterBack(int.Parse(cells[0].Value.ToString()), int.Parse(cells[1].Value.ToString()), cells[2].Value.ToString(), cells[3].Value.ToString());
switch (action)
{
case "update":
//获取相应列的数据ID,弹出加载了该ID数据详细信息的Form,用以修改
StudentLateBackPanelRightUpdate studentLateBackPanelRightUpdate = new StudentLateBackPanelRightUpdate(laterBack);
studentLateBackPanelRightUpdate.Show();
break;
case "delete":
if (MessageBox.Show("确定删除这行数据吗?", "删除提示", MessageBoxButtons.OKCancel) == DialogResult.OK)
{
//获取相应列的数据ID,删除此数据记录
int result = laterBackHelper.delete(laterBack);
if(result > 0)
{
//dataSet.Clear();
dataSet = laterBackHelper.getAllDataSet();
initDataPage(dataSet.Tables[0].Rows.Count,page_step,1);
initView(GetViewDataSet(dataSet,1,page_step));
label_page_count.Text = total_page.ToString();
label_page_range.Text = "1-" + page_step.ToString();
label_all_item_count.Text = total_count.ToString();
}
}
break;
default:
break;
}
}
//获取要显示的数据源
public DataSet GetViewDataSet(DataSet a_ds,int from_index,int end_index)
{
//首先先声明一个DataSet对象和一个DataTable对象
DataSet l_ds = new DataSet();
DataTable l_dt = new DataTable();
//构建DataTable对象的列值
l_dt.Columns.Add("dor_id");//这些列名就是返回的DataSet的列名，可以随意添加
l_dt.Columns.Add("stu_id");
l_dt.Columns.Add("time");
l_dt.Columns.Add("reason");
//遍历传进来的DataSet的值，并对DataTable进行赋值操作
for (int i = from_index - 1; i < end_index ; i++)
{
DataRow dr = l_dt.NewRow();//首先新增一行，然后对其进行赋值
dr["dor_id"] = a_ds.Tables[0].Rows[i][0].ToString().Trim();
dr["stu_id"] = a_ds.Tables[0].Rows[i][1].ToString().Trim();
dr["time"] = a_ds.Tables[0].Rows[i][2].ToString().Trim();
dr["reason"] = a_ds.Tables[0].Rows[i][3].ToString().Trim();
l_dt.Rows.Add(dr);//这里一定要add进去
}
l_ds.Tables.Add(l_dt);//这里也不能忘记
return l_ds;
}
//combobox更改触发事件
private void combobox_selected_listen(object sender, EventArgs e)
{
page_step = int.Parse(comboBox_page_count.SelectedItem.ToString());
textBox_page_count.Text = 1.ToString();
label_page_range.Text = "1-" + page_step.ToString();
total_page = Convert.ToInt16( Math.Ceiling(Convert.ToDouble(total_count) / page_step));
label_page_count.Text = total_page.ToString();
initView(GetViewDataSet(dataSet, 1, page_step));
}
//输入页数变化
private void page_count_change(object sender, EventArgs e)
{
if (textBox_page_count.Text.Equals("")) return;
if (int.Parse(textBox_page_count.Text) < 1)
{
MessageBox.Show("输入页数不能小于1", "系统提示");
return;
}
if (int.Parse(textBox_page_count.Text) > total_page)
{
MessageBox.Show("输入页数超过总页数", "系统提示");
return;
}
current_page_index = int.Parse(textBox_page_count.Text);
var view_range = (current_page_index - 1)* page_step ;
if (view_range + page_step < total_count) {
initView(GetViewDataSet(dataSet, view_range + 1, view_range + page_step));
label_page_range.Text = (view_range + 1).ToString() + "-" + (view_range + page_step).ToString();
}
else {
initView(GetViewDataSet(dataSet, view_range + 1, total_count));
label_page_range.Text = (view_range + 1).ToString() + "-" + total_count.ToString();
}
}
private void button_first_page_Click(object sender, EventArgs e)
{
current_page_index = 1;
var view_range = (current_page_index - 1) * page_step;
initView(GetViewDataSet(dataSet, view_range + 1, view_range + page_step));
label_page_range.Text = (view_range + 1).ToString() + "-" + page_step.ToString();
textBox_page_count.Text = current_page_index.ToString();
}
private void button_previous_page_Click(object sender, EventArgs e)
{
if (current_page_index == 1) return;
current_page_index -= 1;
var view_range = (current_page_index - 1) * page_step;
initView(GetViewDataSet(dataSet, view_range + 1, view_range + page_step));
label_page_range.Text = (view_range + 1).ToString() + "-" + (view_range + page_step).ToString();
textBox_page_count.Text = current_page_index.ToString();
}
private void button_next_page_Click(object sender, EventArgs e)
{
if (current_page_index == total_page) return;
current_page_index += 1;
var view_range = (current_page_index - 1) * page_step;
if (view_range + page_step < total_count)
{
initView(GetViewDataSet(dataSet, view_range + 1, view_range + page_step));
label_page_range.Text = (view_range + 1).ToString() + "-" + (view_range + page_step).ToString();
}
else
{
initView(GetViewDataSet(dataSet, view_range + 1, total_count));
label_page_range.Text = (view_range + 1).ToString() + "-" + total_count.ToString();
}
textBox_page_count.Text = current_page_index.ToString();
}
private void button_last_page_Click(object sender, EventArgs e)
{
current_page_index = total_page;
var view_range = (current_page_index - 1) * page_step;
initView(GetViewDataSet(dataSet, view_range + 1, total_count));
label_page_range.Text = (view_range + 1).ToString() + "-" + total_count.ToString();
textBox_page_count.Text = current_page_index.ToString();
}
}
}
程序运行结果如图4和图5所示，更改每页条数，或者输入页数时都能跳转到相应页面，所有功能都正常，至此，简单的分页功能就实现，如果有任何问题，欢迎给我留言。
图4
图5
