C#实现学员信息管理系统

新手写一段学员信息管理系统，有代码冗余的情况请谅解，代码如下，请大神指点

//登陆入口页面
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;

namespace 学员管理系统
{
 public partial class Lo : Form
 {
 public Lo()
 {
  InitializeComponent();
 }
  string sql= "Data Source=LAPTOP-PCMBBB0N;Initial Catalog=DB_Student;Trusted_Connection=true;";
  private void Log_Load(object sender, EventArgs e)
 {
  this.FormBorderStyle = FormBorderStyle.FixedToolWindow;
  this.Location = new Point(Screen.PrimaryScreen.Bounds.Width / 2 - this.Width / 2, Screen.PrimaryScreen.Bounds.Height / 2 - this.Height / 2);
 }
 Main main;
  private void button1_Click(object sender, EventArgs e)
 {
  try
  {
  string pwd =txtpwd.Text;
  if (pwd.ToString() == "")
  {
   label2.Visible = true;
   label2.Text = "密码不能为空！";
  }
  else
  {
   if (pwd.Equals((table.Rows[0]["Pwd"]).ToString()))
   {
   label2.Visible = false;
   main = new Main();
   main.Show();
   this.Visible = false;
   }
   else
   {
   label2.Text = "密码不正确！";
   label2.Visible = true;
   }
  }
  }
  catch (Exception)
  {
  throw;
  }
 }
 DataTable table = new DataTable();
 private void txtid_Leave(object sender, EventArgs e)
 {
  try
  {
  int id = int.Parse(txtid.Text);
   //1.链接数据库对象
   SqlConnection sqlcon = new SqlConnection(sql);
  //3.创建数据库命令对象
  SqlCommand cmd = new SqlCommand();
  cmd.Connection = sqlcon;
   cmd.CommandText = "SELECT * FROM Student WHERE ID=" + id;
   //5.数据适配器对象
  SqlDataAdapter sda = new SqlDataAdapter();
  sda.SelectCommand = cmd;
  //6.这个table可以用来接受适配的最终结果
  sda.Fill(table);
   if (table.Rows.Count > 0)
  {
   label1.Visible = false;
  }
  else
  {
   label1.Visible = true;
   label1.Text = "输入ID不存在！";
  }
  }
  catch (Exception)
  {

  label1.Visible = true;
  label1.Text = "请输入纯数字ID！";
  txtid.Focus();
  txtid.Text = "";
  }
 }
 private void button2_Click_1(object sender, EventArgs e)
 {
  Register register = new Register();
  register.ShowDialog();
  this.Visible = true;
  label1.Visible = false;
 }
 }
}

//注册页面
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 System.Data.SqlClient;

namespace 学员管理系统
{
 public partial class Register : Form
 {
 public Register()
 {
  InitializeComponent();
 }
 string sql = "Data Source=LAPTOP-PCMBBB0N;Initial Catalog=DB_Student;Trusted_Connection=true;";
  private void button1_Click(object sender, EventArgs e)
 {
  try
  {
  SqlConnection sqlCon = new SqlConnection(sql);
  string sqltxt = string.Format("INSERT INTO Student VALUES('{0}','{1}','{2}','{3}','{4}')", textBox2.Text, textBox1.Text, textBox3.Text, textBox4.Text, textBox5.Text);
  SqlCommand cmd = new SqlCommand(sqltxt, sqlCon);
  sqlCon.Open();
  int res = cmd.ExecuteNonQuery();
  if (res > 0)
  {
   MessageBox.Show("注册成功");
   textBox1.Text = "";
   textBox2.Text = "";
   textBox3.Text = "";
   textBox4.Text = "";
   textBox5.Text = "";
   textBox1.Focus();
  }
  }
  catch (Exception)
  {
  throw;
  }
 }

//信息页面（可以进行数据库信息更改，删除，查看 以及翻页操作）
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 System.Data.SqlClient;
namespace 学员管理系统
{
 public partial class Main : Form
 {
 public Main()
 {
  InitializeComponent();
 }
  string strcon = "Data Source=LAPTOP-PCMBBB0N;Initial Catalog=DB_Student;Trusted_Connection=true;";
 int countPage;
 int nowPage = 1;
 SqlConnection sqlCon;
  private void Main_Load(object sender, EventArgs e)
 {
  sqlCon = new SqlConnection(strcon);
  //绑定页码信息
  try
  {
  string sql = "SELECT COUNT(*) FROM Student";
  SqlCommand cmdl = new SqlCommand(sql, sqlCon);
  sqlCon.Open();
  object res = cmdl.ExecuteScalar();
  if (res != null)
  {
   if ((int)res % 6 > 0)
   {
   countPage = ((int)res / 6) + 1;
   }
   else
   {
   countPage = (int)res / 6;
   }
  }
  }
  catch (Exception)
  {
  throw;
  }
  finally
  {
  sqlCon.Close();
  }
  //初始信息绑定
  try
  {
  SetPage(sqlCon);
  dataGridView1.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill;
  dataGridView1.RowHeadersVisible = false;
  foreach (DataGridViewColumn dc in dataGridView1.Columns)
  {
   dc.SortMode = DataGridViewColumnSortMode.Programmatic;
  }
  dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
  dataGridView1.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
  dataGridView1.ScrollBars = ScrollBars.None;
  dataGridView1.MultiSelect = false;
  dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
  dataGridView1.AllowUserToResizeRows = false;
  dataGridView1.AllowUserToResizeColumns = false;
  dataGridView1.ScrollBars = ScrollBars.None;
  dataGridView1.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill;
  dataGridView1.AllowUserToAddRows = false;
  dataGridView1.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
  dataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
  foreach (DataGridViewColumn item in dataGridView1.Columns)
  {
   item.SortMode = DataGridViewColumnSortMode.NotSortable;
  }
  dataGridView1.ReadOnly = true;
  dataGridView1.CellMouseDown += DataGridView1_CellMouseDown;
  }
  catch (Exception ex)
  {
  throw;
  }
  finally
  {
  sqlCon.Close();
  }
 }
 private void SetPage(SqlConnection sqlCon)
 {
  string sql = string.Format("SELECT ID AS '账号',NAME AS '姓名',Sex AS '性别',Age AS '年龄',Zhanli AS '电话' FROM Student WHERE ID IN(SELECT TOP(6) ID FROM Student WHERE ID NOT IN (SELECT TOP({0}) ID FROM Student ORDER BY ID)ORDER BY ID ) ORDER BY ID", (nowPage - 1) * 6);
  SqlCommand cmd = new SqlCommand(sql, sqlCon);
  SqlDataAdapter sda = new SqlDataAdapter(cmd);
  DataSet ds = new DataSet();
  sda.Fill(ds);
  dataGridView1.DataSource = ds.Tables[0];
  label1.Text = nowPage.ToString();
  label3.Text = countPage.ToString();
 }
  private void DataGridView1_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
 {
  if (e.Button == MouseButtons.Right && dataGridView1.SelectedRows.Count > 0)
  {
  dataGridView1.ClearSelection();
  dataGridView1.Rows[e.RowIndex].Selected = true;
  ID.Idd = (int)dataGridView1.SelectedCells[0].Value;
  contextMenuStrip1.Show();
  }
 }
 private void 删除ToolStripMenuItem1_Click(object sender, EventArgs e)
 {
  try
  {
  SqlConnection sqlCon = new SqlConnection(strcon);
  string sqltxt = "DELETE FROM Student WHERE ID=" + ID.Idd;
  SqlCommand cmd = new SqlCommand(sqltxt, sqlCon);
  sqlCon.Open();
  int res = cmd.ExecuteNonQuery();
  if (res > 0)
  {
   MessageBox.Show("删除成功！");
   Main ma = new 学员管理系统.Main();
   ma.Show();
   this.Visible = false;
  }
  }
  catch (Exception)
  {
  throw;
  }
 }
 private void 修改密码ToolStripMenuItem_Click(object sender, EventArgs e)
 {
  xiugai xiu = new xiugai();
  xiu.ShowDialog();
  this.Visible = false;
 }
 private void 查看详细信息ToolStripMenuItem_Click(object sender, EventArgs e)
 {
  chakan cha = new chakan();
  cha.ShowDialog();
  this.Visible = false;
 }
 private void 下一页ToolStripMenuItem_Click(object sender, EventArgs e)
 {

  if (nowPage >= countPage)
  {
  return;
  }
  else
  {
  nowPage++;
  SetPage(sqlCon);
  }
 }
  private void 上一页ToolStripMenuItem_Click(object sender, EventArgs e)
 {
  if (nowPage <= 1)
  {
  return;
  }
  else
  {
  nowPage--;
  SetPage(sqlCon);
  }
 }
 }
}

/查看详细信息
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;

namespace 学员管理系统
{
 public partial class chakan : Form
 {
 public chakan()
 {
  InitializeComponent();
 }
  private void button1_Click(object sender, EventArgs e)
 {
  Main ma = new 学员管理系统.Main();
  ma.Show();
  this.Visible = false;
 }
 string sql = "Data Source=LAPTOP-PCMBBB0N;Initial Catalog=DB_Student;Trusted_Connection=true;";
 private void chakan_Load(object sender, EventArgs e)
 {
  try
  {
  SqlConnection sqlcon = new SqlConnection(sql);
  string sqltxt = "SELECT * FROM Student WHERE ID="+ID.Idd;
  SqlCommand cmd = new SqlCommand(sqltxt, sqlcon);
  sqlcon.Open();
  SqlDataAdapter sda = new SqlDataAdapter(cmd);
  DataTable table = new DataTable();
  sda.Fill(table);
  Name1.Text = (table.Rows[0]["NAME"]).ToString();
  ID1.Text = (table.Rows[0]["ID"]).ToString();
  Pwd.Text = (table.Rows[0]["Pwd"]).ToString();
  Sex.Text = (table.Rows[0]["Sex"]).ToString();
  Age.Text = (table.Rows[0]["Age"]).ToString();
  Zhanli.Text = (table.Rows[0]["Zhanli"]).ToString();
  }
  catch (Exception)
  {
  throw;
  }
 }
 }
}

//创建一个类用来存储用户账号
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace 学员管理系统
{
 public class ID
 {
 public static int idd;
 public static int Idd
 {
  get
  {
  return idd;
  }
  set
  {
  idd = value;
  }
 }
 }
}

//修改密码
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace 学员管理系统
{
 public partial class xiugai : Form
 {
 public xiugai()
 {
  InitializeComponent();
 }
 string sql = "Data Source=LAPTOP-PCMBBB0N;Initial Catalog=DB_Student;Trusted_Connection=true;";
 private void button1_Click(object sender, EventArgs e)
 {
  string yuan = textBox1.Text;
  string New = textBox2.Text;
  string New2 = textBox3.Text;
  if (yuan=="")
  {
  label4.Visible = true;
  textBox1.Focus();
  }
  else
  {
  if (New=="")
  {
   label5.Visible = true;
   textBox2.Focus();
  }
  else
  {
   if (New2==""||New2!=New)
   {
   label6.Visible = true;
   textBox3.Focus();
   }
   else
   {
   try
   {
    int num = int.Parse(yuan);
    SqlConnection sqlcon = new SqlConnection(sql);
    string sqltext = "UPDATE Student SET Pwd=" + New2 + "WHERE ID="+ID.Idd;
    //string sqltext = "UPDATE StudentInfor SET Pwd=" + New2 + "WHERE ID="+ID.Idd;
    SqlCommand cmd = new SqlCommand(sqltext,sqlcon);
    sqlcon.Open();
    int res = cmd.ExecuteNonQuery();
    if (res>0)
    {
    MessageBox.Show("修改成功");
    }
   }
   catch (Exception)
   {
    throw;
   }
   }
  }
  }
 }
 }
}

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