在展示内容前，先说明一下遇到的几个小问题：
1.在与 SQL Server 建立连接时出现与网络相关的或特定于实例的错误。未找到或无法访问服务器。请验证实例名称是否正确并且 SQL Server 已配置为允许远程连接。 (provider: SQL 网络接口, error: 26 - 定位指定的服务器/实例时出错)。
解决方法：
启动这三个服务。
2.System.Data.SqlClient.SqlException: 用户xxxx 登录失败：
解决方法：
观察连接字符串中是否有这一句：
Integrated Security=True;
当为false时，将在连接中指定用户ID和密码。当为true时，将使用当前的Windows帐户凭据进行身份验证。
参考博客：https://blog.csdn.net/langwen2048/article/details/80116665?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.add_param_isCf&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.add_param_isCf
简化了大佬的做法，自己做的还是比较菜。数据库用的sql server。
登陆界面：
using System;
using System.Data.SqlClient;
using System.Windows.Forms;
namespace WindowsFormsApp1
{
public partial class login : Form
{
public login()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)//登陆按钮
{
String username, password;
username = UserName.Text;
password = Password.Text;
String myconn = "Data Source=(Local);Initial Catalog=Cuser;User ID=sa;Password=tiancaiisme1;";//数据库实例连接字符串
SqlConnection sqlConnection = new SqlConnection(myconn);//新建数据库连接实例
sqlConnection.Open();//打开数据库连接
String sql = "select UserName,Password from users where UserName='" + username + "'and Password='" + password + "'";//SQL语句实现表数据的读取
SqlCommand sqlCommand = new SqlCommand(sql, sqlConnection);
Console.WriteLine(Password);
Console.WriteLine(sql);//控制台输出
SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();
if (UserName.Text == "")
{
MessageBox.Show("请输入用户名", "登陆失败");
UserName.Focus();
}
else if (Password.Text == "")
{
MessageBox.Show("请输入密码", "登陆失败");
}
else
{
if (sqlDataReader.HasRows)//满足用户名与密码一致，进入下一个界面
{
//实现页面跳转
Form1 form3 = new Form1();
this.Hide(); //隐藏当前窗体
form3.ShowDialog();
Application.ExitThread(); //退出当前窗体，这一步很重要，否则最后可能无法将所有进程关闭。最好是在跳转页面后，将之前的页面退出。
}
else//如果登录失败，询问是否注册新用户
{
DialogResult dr = MessageBox.Show("是否注册新用户？", "登录失败", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (dr == DialogResult.Yes)//打开注册界面
{
register form2 = new register();
this.Hide();
form2.ShowDialog();
Application.ExitThread();
}
else
{
UserName.Text = "";
Password.Text = "";
UserName.Focus();
this.Show();
}
}
}
sqlConnection.Close();
}
private void button2_Click(object sender, EventArgs e) //单击注册按钮
{
register form2 = new register();
this.Hide();
form2.ShowDialog();
Application.ExitThread();
}
private void Quit_Click(object sender, EventArgs e) //单击退出按钮
{
Application.Exit();
}
}
}
注册界面：
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.Data.SqlClient;
using System.Windows.Forms;
using System.Security.Cryptography;
namespace WindowsFormsApp1
{
public partial class register : Form
{
public register()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)//注册按钮
{
String username, password, repassword;
username = textBox1.Text;
password = textBox2.Text;
repassword = textBox3.Text;
if (textBox1.Text == "")
{
MessageBox.Show("请输入用户名", "注册失败");
textBox1.Focus();
}
else if (textBox2.Text == "")
{
MessageBox.Show("请输入密码", "注册失败");
textBox2.Focus();
}
else if (textBox3.Text == "")
MessageBox.Show("请确认密码", "注册失败");
else
{
String myConn = "Data Source=(Local);Initial Catalog=Cuser;User ID=sa;Password=tiancaiisme1;";
SqlConnection sqlConnection = new SqlConnection(myConn); //实例化连接对象
sqlConnection.Open();
String sql = "select UserName from users where UserName='" + username + "'";//SQL语句实现表数据的读取
SqlCommand sqlCommand = new SqlCommand(sql, sqlConnection);
SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();
if (sqlDataReader.HasRows)
{
sqlConnection.Close();
MessageBox.Show("该用户名已存在，请重新注册", "注册失败");
textBox1.Text = "";
textBox2.Text = "";
textBox3.Text = "";
textBox1.Focus(); //指定光标在哪个textBox处闪烁
}
else
{
if (password == repassword)//两次输入的密码一致
{
sqlConnection.Close();
string myConn2 = "Data Source=(Local);Initial Catalog=Cuser;User ID=sa;Password=tiancaiisme1;";
SqlConnection sqlConnection2 = new SqlConnection(myConn2); //实例化连接对象
sqlConnection.Open();
//password = GetMD5(password);
String sql2 = "INSERT INTO users(UserName,Password) VALUES('" + username + "','" + password + "')";//SQL语句向表中写入数据
SqlCommand sqlCommand2 = new SqlCommand(sql2, sqlConnection);
sqlCommand2.ExecuteNonQuery();
sqlConnection2.Close();
DialogResult dr = MessageBox.Show("是否返回主界面", "注册成功", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (dr == DialogResult.Yes)//打开注册界面
{
login form2 = new login();
this.Hide();
form2.ShowDialog();
Application.ExitThread();
}
else
{
textBox1.Text = "";
textBox2.Text = "";
textBox3.Text = "";
this.Show();
}
}
else
{
MessageBox.Show("两次输入密码不一致", "错误信息");
textBox1.Text = "";
textBox2.Text = "";
textBox3.Text = "";
}
}
}
}
private void button2_Click(object sender, EventArgs e) //返回登陆按钮
{
login form3 = new login();
this.Hide();
form3.ShowDialog();
Application.ExitThread();
}
}
}