如何在C＃中登录表单失败3次后限制用户 [英] How to restrict a user after 3 unsuccessful attempts in login form in C#

问题描述

private void button1_Click(object sender, EventArgs e)
        {

            if (txtuser.Text == "" && txtpass.Text == "")
            {
                MessageBox.Show("USERNAME and PASSWORD cannot be blank");
                txtuser.Focus();
            }
            else
            {
                SqlConnection cn = new SqlConnection("Data Source=XYZ;Initial Catalog=CRMS;Integrated Security=True");

                cn.Open();
                SqlCommand cmd = new SqlCommand("select * from login where username = '" + txtuser.Text + "' and password = '" + txtpass.Text + "'", cn);
                SqlDataReader dr;
                dr = cmd.ExecuteReader();


                int count = 0;
                while (dr.Read())
                {
                    count += 1;
                }

                if (count == 1)
                {
                    MessageBox.Show("WELCOME!", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
                   
                    Home h = new Home();
                    h.Show();
                    this.Hide();


                }
                else if (count >= 0)
                {
                    MessageBox.Show("Wrong Username or Password", "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }

                cn.Close();

                txtuser.Clear();
                txtpass.Clear();
            }
        }

我的尝试：



以上代码正常运行，完全没问题。我需要的是在3次尝试失败后限制用户，应用程序将退出。我真的不知道在哪里实现它。任何人都可以帮忙，我非常需要。

提前谢谢！

What I have tried:

The above code is working and no problem at all. What I need is to restrict user after 3 unsuccessful attempts and the application will exit. I really don't know where to implement that. Anyone can help please I badly need that.
Thank you in advance!

推荐答案

以下是您的代码的修改版本，以满足您的需求：



1）将计数器移动到表格的全局级别。

2）您可以使用数据阅读器的HasRows来查看是否找到了匹配项。

Hi,

Following is a modified version of your code to suit your needs:

1) Move the counter to a global level of the form.
2) You can use 'HasRows' of the data reader to see if a match was found.

// Move the counter at a global level for the form.
int count = 1;
private void button1_Click(object sender, EventArgs e)
{

    if (txtuser.Text == "" && txtpass.Text == "")
    {
        MessageBox.Show("USERNAME and PASSWORD cannot be blank");
        txtuser.Focus();
    }

    else
    {
        SqlConnection cn = new SqlConnection("Data Source=LAPTOP-SO38VH6F;Initial Catalog=CRMS;Integrated Security=True");
        cn.Open();

        SqlCommand cmd = new SqlCommand("select * from login where username = '" + txtuser.Text + "' and password = '" + txtpass.Text + "'", cn);
        SqlDataReader dr;
        dr = cmd.ExecuteReader();
                
        if (dr.HasRows) // HasRows = true would imply the loging was found.
        {
            MessageBox.Show("WELCOME!", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);

            cn.Close(); // Close connection
            Home h = new Home();
            h.Show();
            this.Hide();
        }
        else
        {
            if (count++ >= 3)
            {
                MessageBox.Show("Failed in 3 login attempts. Assuming unauthorized access. Terminating!", "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
                Application.Exit();
            }

            // This is the ELSE part - not terminating yet, but offering 3 attempts.
            MessageBox.Show("Wrong Username or Password", "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);

            cn.Close(); // Close connection
            txtuser.Clear();
            txtpass.Clear();
        }
    }
}

关于改进代码的一些建议：



1）包裹在TRY中-CATCH。

2）看起来你在数据库中存储密码。请使用加密来存储和检索。

3）Mind Sql Injections。最好将用户名和密码传递给将返回YES / NO的SQL存储过程或函数。

Some suggestions on improving the code:

1) Wrap in TRY-CATCH.
2) It looks like you are storing the password as is in database. Please use encryption to store and retrieve.
3) Mind Sql Injections. Better pass the username and password to a SQL stored procedure or function that will return YES/NO.

本文描述了同样的问题。



三次错误的登录凭据然后登录表单将退出 [ ^ ]

This article describe the same question.

Three times wrong login credentials then login form will exit[^]

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