winform中关于登陆窗口的验证问题!!

Question

SqlConnection thisConnection = new SqlConnection(@"Server=.;Database=master; Integrated Security=True;");
                thisConnection.Open();
                SqlCommand thisCommand = thisConnection.CreateCommand();
                thisCommand.CommandText = "Select userName,password from userInf";
                SqlDataReader thisReader = thisCommand.ExecuteReader();
                //验证用户名和密码
                while (thisReader.Read())
                {
                    if (thisReader["userName"].ToString() == userNameTextBox.Text)
                    {
                        if (thisReader["password"].ToString() == passwordTextBox.Text)
                        {
                            Form2 frm = new Form2();
                            frm.ShowDialog();
                        }
                        else
                        {
                            MessageBox.Show("密码错误，请重新输入！", "登陆", MessageBoxButtons.OK, MessageBoxIcon.Information);
                            passwordTextBox.Text = "";
                            this.passwordTextBox.Focus();
                        }
                    }
                    else
                    {
                        MessageBox.Show("该用户名不存在，请重新输入！", "登陆", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        userNameTextBox.Text = "";
                        this.userNameTextBox.Focus();                    }
  上述写法在验证时循环有问题,在SQL表中循环验证输入的用户名和密码该如何写法?

Answer 1

查询时用SQL加WHERE条件检索
即把你上面的SQL语句 + Where 用户名/密码 =TextBox的值
然后thisReader.Read()就可以知道有没有记录

Answer 2

bool bl = false;
  while (thisReader.Read()) 
                { 
                    if (thisReader["userName"].ToString() == userNameTextBox.Text) 
                    { 
                        if (thisReader["password"].ToString() == passwordTextBox.Text) 
                        { 
                            Form2 frm = new Form2(); 
                            frm.ShowDialog(); 
                            bl = true;
                        } 
                    } 
}if(!bl )
{
MessageBox.Show("密码错误，请重新输入！", "登陆", MessageBoxButtons.OK, MessageBoxIcon.Information); 
                        this.userNameTextBox.Text = ""; 
                        this.userNameTextBox.Focus(); }

Answer 3

SqlConnection thisConnection = new SqlConnection(@"Server=.;Database=master; Integrated Security=True;"); 
thisConnection.Open(); 
SqlCommand thisCommand = thisConnection.CreateCommand(); 
thisCommand.CommandText = "Select count(*) from userInf where userName='" + userNameTextBox.Text + "' and password='" + passwordTextBox.Text + "'"; 
int count=Convert.ToInt32(command.ExecuteScalar());  //command.ExecuteScalar()返回查询结果的第一行第一列，忽略其他的
if(count==1)
{
//成功
}
else
{
//姓名密码错误
}//如果你只查询姓名的话 查询语句的条件就跟一个姓名就可以了

Answer 4

SqlDataReader usdr = FPara.SqlReader("select top 1 * from lampUserName where UserName='" + UserCode + "'", FPara.connStr);
                    if (usdr != null)
                    {
                        if (usdr.Read())
                        {
                            if (usdr["Pswd"].ToString() != UserPswd)
                            {
                                MessageBox.Show("密码错误");
                            }
                            else
                            {
                               
                                FPara.ShopCode = usdr["UserName"].ToString();
                                MessageBox.Show("登录成功");
                                this.Hide();
                                Form4 f = new Form4();
                                f.Show();
                                                            }
                        }
                        else
                        {
                            MessageBox.Show("帐号密码错误");
                        }
                        usdr.Close();
                    }
                    else
                    {
                        MessageBox.Show("无法连接数据库,请检查相关环境");
                        Application.Exit();
                        this.Close();
                    }