Question

我是一名C＃学习者，需要您的帮助。提前致谢。我正在处理此多用户单次登录表单。我已连接到SQL本地数据库，其中包含以下内容：用户名，密码，用户类型

我的问题是，只要这三个是正确的，下面的代码就可以正常工作。例如，如果我输入了错误的密码，则不会发生任何事情。

我的代码的“ Else”部分一定存在问题，但是我尝试了很多更改，甚至在我接近使之工作时也失去了跟踪。请帮忙。重申我对项目的期望： 1.从组合框（cmbusertype）中选择“管理员”或“学生”并提供不正确的用户名和密码时，我会收到不正确的凭据错误消息和尝试次数。3次尝试后，登录按钮应显示为灰色，并提示我重置我的密码。

public partial class Loginsystem : Form
{
    public Loginsystem()
    {
        InitializeComponent();
    }
    int attempts =1;
    private void btnlogin_Click(object sender, EventArgs e)
    {
        if (cmbusertype.SelectedItem == null)
        {
            MessageBox.Show("Please select User Type to continue...");
            cmbusertype.Focus();
            return;
        }
        if (txtuserid.Text == "")
        {
            MessageBox.Show("Please enter your UserID...");
            txtuserid.Focus();
            return;
        }
        if (txtpassword.Text == "")
        {
            MessageBox.Show("Please enter your password...");
            txtpassword.Focus();
            return;
        }

        try
        {
            SqlConnection con = new SqlConnection(@"Data Source = (LocalDB)\MSSQLlocaldb; Initial Catalog = AdminAuthentication; Integrated Security = True"); ;
            SqlCommand cmd = new SqlCommand("select * from SimplifyLogin where userID='" + txtuserid.Text + "' and password='" + txtpassword.Text + "'", con);
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            sda.Fill(dt);
            string cmbItemValue = cmbusertype.SelectedItem.ToString();
            if (dt.Rows.Count >0)
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {

                    if (dt.Rows[i]["UserType"].ToString() == cmbItemValue) //you can use 2 instead of usertype in that index because usertype column is in 2 index
                    {
                        if (cmbusertype.SelectedIndex == 0)
                        {
                            MessageBox.Show("You are logged in as " + dt.Rows[i][2]);
                            MessageBox.Show("Displaying Admin Dashboard");
                            this.Hide();
                        }

                        else
                        {
                            MessageBox.Show("Welcome Student! Displaying Exam Options");
                            this.Hide();
                        }
                    }
                    else
                    {
                        MessageBox.Show("Invalid username and/or Password.Please try again. \nAttempts: " + attempts + "out of of 3");
                        txtpassword.Clear();
                        attempts++;
                    }

                    if (attempts == 4)
                    {
                        MessageBox.Show("You have reached maximum login attempts. Click 'Forgot Password' below to reset it.");
                        btnlogin.Enabled = false;

                    }
                }
            }
        }

        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }
}

}

Answer 1

我可以自定义此代码，因为您不必使用for循环，因为从数据库返回的行数仅是一个。.

public partial class Loginsystem : Form {
public Loginsystem() {
    InitializeComponent();
}
private int attempts = 1;
private void btnlogin_Click(object sender, EventArgs e) {
    if (cmbusertype.SelectedItem == null) {
        MessageBox.Show("Please select User Type to continue...");
        cmbusertype.Focus();
        return;
    }
    if (txtuserid.Text == "") {
        MessageBox.Show("Please enter your UserID...");
        txtuserid.Focus();
        return;
    }
    if (txtpassword.Text == "") {
        MessageBox.Show("Please enter your password...");
        txtpassword.Focus();
        return;
    }
    try {
      SqlConnection con = new 
      SqlConnection(@"Data Source = (LocalDB)\MSSQLlocaldb; Initial Catalog = AdminAuthentication; Integrated Security = True"); ;
      SqlCommand cmd = new SqlCommand("select * from SimplifyLogin where userID='" + txtuserid.Text + "' and password='" + txtpassword.Text + "'", con);
      SqlDataAdapter sda = new SqlDataAdapter(cmd);
      DataTable dt = new DataTable();
      sda.Fill(dt);
      string cmbItemValue = cmbusertype.SelectedItem.ToString();
      if (dt.Rows.Count > 0) {

        if(dt.Rows[0]["UserType"].ToString() == cmbItemValue) {

          if (cmbusertype.SelectedIndex == 0 ) {
            MessageBox.Show("You are logged in as " + dt.Rows[0][2] + Environment.NewLine + "Displaying Admin Dashboard"); 
            this.Hide();
          } else {
            MessageBox.Show("Welcome Student! Displaying Exam Options");
            this.Hide();
          }
       } else {
            MessageBox.Show("Invalid username and/or Password.Please try again. \nAttempts: " + attempts + "out of of 3");
            txtpassword.Clear();
            attempts++;
            if (attempts == 4) {
              MessageBox.Show("You have reached maximum login attempts. Click 'Forgot Password' below to reset it.");
              btnlogin.Enabled = false;
            }
      }
    } catch (Exception ex) {
         MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
   }
 }

Answer 2

我今天早上想通了：

这是我所做的更改：

摆脱了一个嵌套的ifs

if（（（dt.Rows [i] [“ UserType”]。ToString（）== cmbItemValue）&&（cmbusertype.SelectedIndex == 0））

将}调整为必要。

多用户登录，跟踪登录尝试

2 个答案: