C# 连接数据库 登录窗体，的代码，主要就是查询 用户名和密码的语句

Question

RT

Answer 1

建议，将数据连接放在App.config里：
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
  </configSections>
  <connectionStrings>
    <add name="【自定义连接名称 如：SQLDBConnectionString(数据库名称+ConnectionString)】"
        connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\【数据库文件如：SqlDB.mdf】;Integrated Security=True;User Instance=True;Asynchronous Processing=true"
        providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>然后窗体里（调用app.config的数据库连接）：String connStr = ConfigurationManager.ConnectionStrings["【自定义连接名称 如：SQLDBConnectionString(数据库名称+ConnectionString)】"].ConnectionString;然后接下去就是验证登录了：
using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "SELECT * FROM 【表】 where PassWord=@PassWord and UserName=@UserName";
                    cmd.Parameters.Add(new SqlParameter("UserName", txtName.Text));
                    cmd.Parameters.Add(new SqlParameter("PassWord", txtPass.Text));
                    int i = Convert.ToInt32(cmd.ExecuteScalar());
                    if (i > 0)
                    {                    }
                    else
                    {
                        MessageBox.Show("用户名/密码错误！");
                    }
                }
            }

Answer 2

登录按钮：private void button1_Click(object sender, EventArgs e)
        {
            if ( textBox2.Text.Trim() == "" || textBox3.Text.Trim() == "")
            {
               MessageBox.Show("提示：请输入登录用户名和密码！", "警告");
            }
            else 
            {              
                SqlConnection connect = DB.DB_Login();
                string strSQL = "select * from 表名 where Login='" + textBox2.Text.Trim() + "'and Password='" + textBox3.Text.Trim() + "'";
                SqlCommand cmd = new SqlCommand(strSQL, connect);
                SqlDataReader asd = cmd.ExecuteReader();
                asd.Read();
                if (asd.HasRows)
                {
                   this.Hide();
                   MainForm formchild = new MainForm();
                   formchild.users = textBox2.Text.Trim();
                   formchild.Show();
                }
                else
                {
                        MessageBox.Show("提示：学生用户名或密码错误！", "警告");
                }
                   connect.Close();
                }               
            }
        }
DB类的DB_Login()：  public static SqlConnection DB_Login()
        {
            SqlConnection connect = new SqlConnection("Data Source=(local);Database=FingerPrint;UID=sa;PWD=123;数据库名");
            connect.Open();
            return connect;
        }   
楼主上分。分 。。分 

Answer 3

建议用 【字段=@自定义名】然后【cmd.Parameters.Add(new SqlParameter("自定义名", TextBox1.Text));
】：
 cmd.CommandText = "SELECT * FROM 【表】 where PassWord=@PassWord and UserName=@UserName";
                    cmd.Parameters.Add(new SqlParameter("UserName", txtName.Text));
                    cmd.Parameters.Add(new SqlParameter("PassWord", txtPass.Text));
可以防止SQL注入攻击。

Answer 4

 private void button1_Click(object sender, EventArgs e)
        {
            string strconn = "server=(local);uid=sa;pwd=123;database=login";
            SqlConnection conn=new SqlConnection(strconn);
            string userName =txtUserName.Text.ToString().Trim();
            string userPwd = txtPwd.Text.ToString().Trim();
            string selectStr = "Select * from login where name = '" + userName + "'";
            SqlCommand cmd = new SqlCommand(selectStr, conn);
            try
            {
                conn.Open();                    //打开连接
                SqlDataReader sdr = cmd.ExecuteReader(); //执行查询
                if (sdr.Read())                 //如果该用户存在
                {
                    if (sdr.GetString(1).Trim() == userPwd) //密码正确
                    {
                    //Session["userName"] = userName;
                   // Session["userRole"] = userRole;
                        conn.Close();
                        //lblMessage.Text = "恭喜你！";
                        Form2 form = new Form2();
                        form.ShowDialog();                    }
                    else                        //密码错误，给出提示信息！
                    {
                        lblMessage.Text = "您输入的密码错误，请检查后重新输入！";
                    }
                }
                else                            //用户不存在或用户名输入错误
                {
                    lblMessage.Text = "该用户不存在或用户名输入错误，请检查后重新输入！";
                }
            }
            catch (Exception ee)
            {
                //Response.Write("<script language=javascript>alert('" + ee.Message.ToString() + "')</script>");
            }
            finally
            {
                conn.Close();
            }
 
        }

Answer 5

up 要是能给源文件就好了。[email protected]