使用C#开发数据库应用系统

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 第一章 { public partial class frmMain : Form { //连接字符串 private const string sqlcon = "Data Source=.;Initial Catalog=MySchool;User ID=sa;Pwd=."; //用于打开/关闭数据库连接 SqlConnection con = new SqlConnection(sqlcon); //构造方法：用来做初始化工作 public frmMain() { InitializeComponent(); } //取消按钮的单击事件 private void btnexit_Click(object sender, EventArgs e) { DialogResult result= MessageBox.Show("是否取消？","提示",MessageBoxButtons.YesNo); if (result == DialogResult.Yes) { //关闭窗体 this.Close(); } else { //清空窗体中所有信息 this.txtName.Clear(); this.txtPwd.Clear(); this.cborow.SelectedIndex = -1 ; } } //登录按钮的单击事件 private void btnOK_Click(object sender, EventArgs e) { if (CheckInput()) { try { con.Open(); string sql = "select count(*) from Student where StudentNo=‘" + this.txtName.Text + "‘ and LoginPwd=‘" + this.txtPwd.Text + "‘"; SqlCommand com = new SqlCommand(sql, con); int count = (int)com.ExecuteScalar(); if (count > 0) { MessageBox.Show("登陆成功！", "提示"); //创建出FrmTest窗体 FrmTest test = new FrmTest(); //test代表的就是FrmTest窗体 .Test就是标题 test.txtshow.Text = "欢迎您：" + this.txtName.Text; test.Show(); } else { MessageBox.Show("登陆失败！", "提示"); this.txtName.Clear(); this.txtPwd.Clear(); this.cborow.SelectedIndex = -1; } } catch (Exception ex) { Console.WriteLine(ex); } finally { con.Close(); } } } //在点击登录按钮的时候验证文本框内容是否为空 private bool CheckInput() { bool flag = true; //判断文本框是否输入值了？ //判断txtName是否输入值了 if (this.txtName.Text.Trim()== null||this.txtName.Text.Trim() =="") { //提示信息 MessageBox.Show("请输入登录账号！","登录验证"); flag = false; }else if (this.txtPwd.Text.Trim() == null || this.txtPwd.Text.Trim() == "") { //提示信息 MessageBox.Show("请输入登录密码！", "登录验证"); flag = false; } else if (this.cborow.Text.Trim() == null || this.cborow.Text.Trim() == "") { MessageBox.Show("请选择登录角色！", "登录验证"); flag = false; } return flag; } } }

 

使用C#开发数据库应用系统

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