最近看见好多人都在写这个，但他们用的都是用户名登录，如果用户名太长，那就太麻烦了。

第一步：按照网上的教程建表。并在表中手动输入一条数据。

第二步：在Form1.cs（登录界面）自定义一个判断密码用户名是否正确的方法:

public int Ex(string sql){SqlCommand com = new SqlCommand(sql, conn);if (conn.State == ConnectionState.Closed)conn.Open();com.CommandType = CommandType.Text;int result = Convert.ToInt32(com.ExecuteScalar());conn.Close();return result;}

再定义一个GetDataSet方法，用于查询用户名。

public static DataSet GetDataSet(string sql1){SqlDataAdapter sqlda = new SqlDataAdapter(sql1,conn);DataSet ds = new DataSet();sqlda.Fill(ds);return ds;}

ID输入框的代码如下

private void textBox1_KeyPress(object sender, KeyPressEventArgs e){if (char.IsDigit(e.KeyChar) || (e.KeyChar == '\r' || (e.KeyChar == '\b')))e.Handled = false;elsee.Handled = true;}

判断输入是否合理方法代码如下：

private bool ValidateInput(){if (textBox1.Text.Trim() == ""){MessageBox.Show("请输入登录账号");}else if (int.Parse(textBox1.Text.Trim()) > 65535)MessageBox.Show("请输入正确的登录账号");else if (textBox1.Text.Trim().Length > 5 && textBox2.Text.Trim() == "")MessageBox.Show("请输入密码");return true;}

登录按钮事件代码如下：

if (ValidateInput()){try{if(conn.State == ConnectionState.Open){conn.Dispose();conn.Close();}int id = int.Parse(textBox1.Text.Trim());string sql = "select count(*) from tb_User where ID=" + id + " and Pwd = '" + textBox2.Text + "'";int num = Ex(sql);if (num == 1){UserID = int.Parse(textBox1.Text.Trim());this.Hide();Form2 Form21 = new Form2();Form21.Show();}else{MessageBox.Show("用户Id或密码不正确");}}catch(Exception ex){MessageBox.Show("未能连接到服务器","提示");}}

别忘了在

public Form1()
        {
            InitializeComponent();
        }

的下面添加

public static int UserID = 0;public static SqlConnection conn = new SqlConnection(@"Data Source=DESKTOP-GNQACEJ\Gres;Integrated Security=True;DataBase=Server");

新建一个主窗体，在主窗体中写入代码:

public static string PeopleName;private void Form2_Load(object sender, EventArgs e){PeopleName = Form1.GetDataSet("select Name from tb_User where ID=" + Form1.UserID).Tables[0].Rows[0][0].ToString();label1.Text = PeopleName + "\n(" + Form1.UserID + ")";label2.Text = Form1.GetDataSet("select Text from tb_User where ID=" + Form1.UserID).Tables[0].Rows[0][0].ToString();if(label1.Text.Trim().Length < 1){label2.Text = "无个性签名";}}

程序最终运行效果：Form1

 Form2