VB.NET SQL数据库登录

Question

I have a database login working with use of a MySQL database. The user is brought to a menu screen if their login is successful. Everything works fine but what I'm trying to do is bring the user to a separate admin screen if their "UserGroup" field in the database says "Admin"

I'm stuck so far, the working code for everything is as follows:

Imports MySql.Data.MySqlClient

Public Class frmLogin
    Dim MysqlConn As MySqlConnection
    Dim command As MySqlCommand
    Dim reader As MySqlDataReader

    Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click

        MysqlConn = New MySqlConnection
        MysqlConn.ConnectionString =
        "server=localhost;port=3307;userid=root;password=Djmmcm93;database=dojodb"

        Dim reader As MySqlDataReader ' had to be declared inside the button or would not work


        Try
            MysqlConn.Open() ' opening the connection to the DB
            Dim query As String
            query = "select * from dojodb.userinfo where UserID='" & txtUserID.Text & "' and Password='" & txtPassword.Text & "'"
            command = New MySqlCommand(query, MysqlConn)
            reader = command.ExecuteReader 'executes the command and reads data from db

            Dim count As Integer
            count = 0
            While reader.Read
                count = count + 1
            End While

            If count = 1 Then
                MessageBox.Show("Welcome!")
                Me.Hide()
                frmUserMenu.Show()
            ElseIf count > 1 Then
                MessageBox.Show("username and password are duplicated!") 'Only here as test
            Else
                MessageBox.Show("username and password are incorrect!")
            End If

            MysqlConn.Close()

        Catch ex As Exception
            MessageBox.Show(ex.Message) 'printing the exact error to help future testing if needed
        Finally
            MysqlConn.Dispose()
        End Try
    End Sub
End Class

Answer 1

The first thing I noticed and changed was SELECT *. For performance reasons, you should try never to select * and specify columns you want. If there are more columns, feel free to add them.

Then I adjusted your code, hopefully it helps you:

Public Class frmLogin
    Dim MysqlConn As MySqlConnection
    Dim command As MySqlCommand
    Dim reader As MySqlDataReader

    Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click

        MysqlConn = New MySqlConnection
        MysqlConn.ConnectionString =
        "server=localhost;port=3307;userid=root;password=Djmmcm93;database=dojodb"

        Dim reader As MySqlDataReader ' had to be declared inside the button or would not work


        Try
            MysqlConn.Open() ' opening the connection to the DB
            Dim query As String
            query = "select UserID,Password from dojodb.userinfo where UserID='" & txtUserID.Text & "' and Password='" & txtPassword.Text & "'"
            Dim userStatus = "select UserGroup from dojodb.userinfo where UserID='" & txtUserID.Text & "' and Password='" & txtPassword.Text & "'"
            command = New MySqlCommand(query, MysqlConn)
            reader = command.ExecuteReader 'executes the command and reads data from db

            If UserGroup = "Admin" Then

                'Send to admin page here


            Else            

                Dim count As Integer
                count = 0
                While reader.Read
                count = count + 1
                End While

                If count = 1 Then
                MessageBox.Show("Welcome!")
                Me.Hide()
                frmUserMenu.Show()
                ElseIf count > 1 Then
                MessageBox.Show("username and password are duplicated!") 'Only here as test
                Else
                MessageBox.Show("username and password are incorrect!")
                End If

                MysqlConn.Close()
            End If

        Catch ex As Exception
            MessageBox.Show(ex.Message) 'printing the exact error to help future testing if needed
        Finally
            MysqlConn.Dispose()
        End Try
    End Sub
End Class

Answer 2

You can try to modify the next portion of your code:

Dim count As Integer
Dim UserGroup As String = ""   ' <───────  Insert this line.
count = 0
While reader.Read
    count = count + 1
    UserGroup = reader("UserGroup").ToString   ' <───────  Insert this line ("UserGroup" is the name of the field in the UserInfo table).
End While

If count = 1 Then
    MessageBox.Show("Welcome!")

    If UserGroup = "Admin" Then   ' ' <───────  Insert this If to verified UserGroup.
        ' bring the user to separate admin screen
    Else
        Me.Hide()
        frmUserMenu.Show()
    End If
ElseIf count > 1 Then
    MessageBox.Show("username and password are duplicated!") 'Only here as test
Else
    MessageBox.Show("username and password are incorrect!")
End If