帮助vb.net代码，该代码不允许某些用户进入系统 [英] help vb.net code that does not allow some users to enter the system

问题描述

嗨
我在我的项目上使用vb.net，并且我需要有关(不允许某些用户进入系统的代码)的帮助

我有一个登录表单，其中包含(2个用于输入用户名的文本框和用于登录系统的登录+按钮)
我也有用于登录的数据库表，其中有(用户名+密码+ user_type + record_status)


问题是((((如果用户被管理员删除，则他无法进入系统)))

但是我该怎么做呢?

她是我的代码:

 尝试
            Dim  dt  As  字符串
           dt =现在
           icount = " 
           Mycn = 新建 SqlConnection(" )

           Mycn.Open()
           '  SQLstr =从登录名中选择Userlevel，其中user_name ='"& txtname.Text.Trim& 'and password ='"& txtpass.Text.Trim& " 
           SQLstr = " & txtname.Text.Trim& " & txtpass.Text.Trim& " 

           命令= 新建 SqlCommand(SQLstr，Mycn)
           icount = command.ExecuteScalar


           如果 icount = "  然后
               My.Computer.Audio.Play(My.Resources.Windows_Error，AudioPlayMode.Background)
               MessageBox.Show(" ，" 登录..."，MessageBoxButtons.OK，MessageBoxIcon.Information)



           其他

               usrID = txtname.Text.Trim



               My.Computer.Audio.Play(My.Resources.car，AudioPlayMode.Background)
               Timer1.Start()
               Timer2.Start()

           结束 如果

           如果 icount.Trim<> "  然后

               mainpageadmin.SystemSettingToolStripMenuItem.Enabled = 错误

           结束 如果

       捕获，例如 As 异常
           MessageBox.Show(例如Message& " )

           Mycn.Close()


       结束 尝试

       如果 icount.Trim<> "  然后
           MessageBox.Show(" ，" ，MessageBoxButtons.OK，MessageBoxIcon.Information)
       结束 如果

       Mycn.Close()

解决方案

好吧，你是一个初学者，所以...一步一步...

STEP 1)
要使用登录"表单构建应用程序，我们需要创建自定义类 [界面 [ ' 这是我们班级的界面 公共 界面 IMyApp 功能 CheckUser( ByVal sUName As 字符串， ByVal sUPwd As As 属性 UserName() As 字符串 结束 界面

===类===

 ' 这是我们的类，它从接口中实现方法和属性
公共 类 TMyApp
    实现 IMyApp

    ' 如何建立连接字符串? 
    '  http://www.connectionstrings.com/
     Const  sConn  As  字符串 = " 

     Dim  oConn  As  SqlClient.SqlConnection = 没什么
     Dim  sUserName  As  字符串 = 字符串.空

    公共 子 新建()
        ' 在这里您可以启动一些属性... 
    结束 子

    公共 功能 CheckUser( ByVal  sUName  As  字符串， ByVal  sUPwd 字符串)整数 实现 IMyApp.CheckUser
         Dim  oComm  As  SqlClient.SqlCommand = 没什么
         Dim  oRdr  As  SqlClient.SqlDataReader = 没什么
         Dim  oDt  As  Data.DataTable = 没什么
         Dim  sSQL  As   String  = 字符串.空
         Dim  iRetVal  As  整数 =  0 

        尝试
            oConn = 新建 SqlClient.SqlConnection(sConn)
            oConn.Open()
            sSQL = " & vbCr& _
                    " & vbCr& _
                    " 
            oComm = 新建 SqlClient.SqlCommand(sSQL，oConn)
            使用 oComm
                .CommandType = CommandType.Text
                .Parameters.AddWithValue(" ，sUName)
                .Parameters.AddWithValue(" ，sUPwd)
                oRdr = .ExecuteReader()
            结束 使用
            oDt = 新建 Data.DataTable()
            oDt.Load(oRdr)
            iRetVal = oDt.Rows.Count
            选择 案例 iRetVal
                案例  0 
                    ' 未知用户或用户不存在
                    MsgBox(" ，MsgBoxStyle.Information，" )
                    退出 尝试
                案例  1 
                    ' 是的，欢迎
                    sUserName = sUName
                案例 其他
                    MsgBox(" "  信息...")
                    ' 超过1位用户，有可能吗?
            结束 选择

        捕获，例如 As  Data.DataException
            iRetVal = -1
            MsgBox(例如消息，MsgBoxStyle.Exclamation，" )
        捕获，例如 As  SqlClient.SqlException
            iRetVal = -1
            MsgBox(例如消息，MsgBoxStyle.Exclamation，" )
        捕获，例如 As 异常
            iRetVal = -1
            MsgBox(例如消息，MsgBoxStyle.Exclamation，" )

        最后
            oDt = 没什么
            oRdr.Close()
            oRdr = 什么都没有
            oComm.Dispose()
            oComm = 没什么
            如果 oConn.State = ConnectionState.打开然后 oConn.Close()
            oConn = 没什么
        结束 尝试

        返回 iRetVal
    结束 功能

    公共 属性 UserName() As  字符串 实现 IMyApp.UserName
        获取
            返回 sUserName
        结束 获取
        设置( ByVal 值 As  字符串)
            sUserName =值
        结束 设置
    结束 属性

    受保护的 替代  Sub  Finalize()
         MyBase  .Finalize()
    结束 子

结束 类 

STEP 2)
现在，我们需要将我们的类声明为全局变量.为什么?要使其"可见 [ ===模块===

 模块 MainMod
    ' 这是一个可以存储全局变量的地方

    ' 看看该过程:MainFrm.New()
    公共 oMyApp  As  IMyApp = 什么都没有

结束 模块 

STEP 3
登录时间
===登录表单类===

 公共 类 LoginFrm

    私有 子 OK_Click( ByVal 发​​件人 As 系统.对象， ByVal  e  As  System.EventArgs)句柄确定.单击
         Dim  iCount  As  整数 =  0 
        如果 我 .UsernameTextBox.Text.Length =  0  或 _
            我 .PasswordTextBox.Text.Length =  0  >然后
            MsgBox(" ，MsgBoxStyle.Information， 错误")
            退出 子
        结束 如果

        iCount = MainMod.oMyApp.CheckUser(我 .UsernameTextBox.Text， Me  .PasswordTextBox.Text)
        选择 案例 iCount =  1 
            案例  0 
                ' 未知用户
                我 .OK.DialogResult = Windows.Forms.DialogResult.Abort
            案例  1 
                ' 确定
                我 .OK.DialogResult = Windows.Forms.DialogResult.OK
            案例 其他
                ' 多个用户?
                我 .OK.DialogResult = Windows.Forms.DialogResult.Cancel
        结束 选择

        我 .Close()
    结束 子

    私有 子 Cancel_Click( ByVal 发​​件人 As 系统.对象， ByVal  e  As  System.EventArgs)句柄取消.单击
        我 .Close()
    结束 子

    私有 子 LoginFrm_Load( ByVal 发​​件人 As 系统.对象， ByVal  e  As  System.EventArgs)句柄  MyBase  .Load
        我 .UsernameTextBox.Text = Environ(" )
    结束 子
结束 类 

STEP 4
===主表单类===

 公共 类 MainFrm

    公共 子 新建()
         Dim  dlgRes  As  DialogResult = Windows.Forms.DialogResult.OK
        '  Windows窗体设计器需要此调用.
        InitializeComponent()
        ' 在InitializeComponent()调用之后添加任何初始化.

        ' 通过界面启动我们的课程，看看MainMod.vb 
        oMyApp = 新 TMyApp
        ' 循环调用LoginFrm 
        做
            dlgRes = LoginFrm.ShowDialog()
            ' 如果用户取消登录，则跳过初始化初始化
            如果 dlgRes = Windows.Forms.DialogResult.Cancel 然后 退出 子
            ' 欢迎；)
            如果 dlgRes = Windows.Forms.DialogResult.OK  And  oMyApp.UserName< 字符串.空然后 退出 执行
            ' 未知用户-看一下LoginFrm.vb 
        循环，直到dlgRes = Windows.Forms.DialogResult.Abort

        ' 简单的初始化:)
        我 .LblInfo.Text = " & oMyApp.UserName& " 

    结束 子

    受保护的 替代  Sub  Finalize()
        oMyApp = 没什么
         MyBase  .Finalize()
    结束 子

结束 类 

也许这不是最佳编码(尤其是登录的一部分)，所以我说:对不起.
最重要的想法是:显示简单有效的示例.

希望对您有所帮助；)

hi
i am using vb.net on my project and i want help on the (code that does not allow some users to enter the system)

i have a form for login which contain( 2 textboxes for username and login + button for sign in to the system)
also i have database table for login which have (username+ password + user_type + record_status)


the problem is (((if the user is deletet by admin then he can not enter the system)))

but how can i do this succsesfuly??

her is my code:

Try
           Dim dt As String
           dt = Now
           icount = ""
           Mycn = New SqlConnection("Data Source=IMAN-PC;Initial Catalog=control car;Integrated Security=True")

           Mycn.Open()
           'SQLstr = "select Userlevel from login where user_name='" & txtname.Text.Trim & "' and password='" & txtpass.Text.Trim & "' "
           SQLstr = "select Userlevel , record_statuse from login where user_name='" & txtname.Text.Trim & "' and password='" & txtpass.Text.Trim & "'"

           command = New SqlCommand(SQLstr, Mycn)
           icount = command.ExecuteScalar


           If icount = "" Then
               My.Computer.Audio.Play(My.Resources.Windows_Error, AudioPlayMode.Background)
               MessageBox.Show("Invalid UserName or Password", "Login...", MessageBoxButtons.OK, MessageBoxIcon.Information)



           Else

               usrID = txtname.Text.Trim



               My.Computer.Audio.Play(My.Resources.car, AudioPlayMode.Background)
               Timer1.Start()
               Timer2.Start()

           End If

           If icount.Trim <> "Admin" Then

               mainpageadmin.SystemSettingToolStripMenuItem.Enabled = False

           End If

       Catch ex As Exception
           MessageBox.Show(ex.Message & "Could NOT Login")

           Mycn.Close()


       End Try

       If icount.Trim <> "A" Then
           MessageBox.Show("You can not enter the system because you are deleted by ADMINISTRATOR", "Login...", MessageBoxButtons.OK, MessageBoxIcon.Information)
       End If

       Mycn.Close()

解决方案

OK, you''re a beginner, so... step by step...

STEP 1)
To build an application with Login form, we need to create custom class[^] and interface[^] to communicate between application and our class.

Before you start programming, please, read carefully articles (links above) about interfaces and classes.

=== interface ===

'This is an interface for our class
Public Interface IMyApp
    Function CheckUser(ByVal sUName As String, ByVal sUPwd As String) As Integer
    Property UserName() As String
End Interface

=== class ===

'This is our class, which implements methods and properties from our interface
Public Class TMyApp
    Implements IMyApp

    'how to build connection string? 
    'http://www.connectionstrings.com/
    Const sConn As String = "Data Source=YOUR_SQL_SERVER;Initial Catalog=YOUR_DATABASE;Integrated Security=True"

    Dim oConn As SqlClient.SqlConnection = Nothing
    Dim sUserName As String = String.Empty

    Public Sub New()
        'here you can initiate some properties...
    End Sub

    Public Function CheckUser(ByVal sUName As String, ByVal sUPwd As String) As Integer Implements IMyApp.CheckUser
        Dim oComm As SqlClient.SqlCommand = Nothing
        Dim oRdr As SqlClient.SqlDataReader = Nothing
        Dim oDt As Data.DataTable = Nothing
        Dim sSQL As String = String.Empty
        Dim iRetVal As Integer = 0

        Try
            oConn = New SqlClient.SqlConnection(sConn)
            oConn.Open()
            sSQL = "SELECT * " & vbCr & _
                    "FROM [YOUR_DATABASE].[dbo].[TABLE]" & vbCr & _
                    "WHERE login=@UName AND pwd=@UPwd"
            oComm = New SqlClient.SqlCommand(sSQL, oConn)
            With oComm
                .CommandType = CommandType.Text
                .Parameters.AddWithValue("@UName", sUName)
                .Parameters.AddWithValue("@UPwd", sUPwd)
                oRdr = .ExecuteReader()
            End With
            oDt = New Data.DataTable()
            oDt.Load(oRdr)
            iRetVal = oDt.Rows.Count
            Select Case iRetVal
                Case 0
                    'unknown user or user doesn't exist
                    MsgBox("Unknow user or user doesn't exists!", MsgBoxStyle.Information, "Information...")
                    Exit Try
                Case 1
                    'YES, welcome
                    sUserName = sUName
                Case Else
                    MsgBox("More than one user???", MsgBoxStyle.Information, "Information...")
                    'more than 1 user, is it possible???
            End Select

        Catch ex As Data.DataException
            iRetVal = -1
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Error...")
        Catch ex As SqlClient.SqlException
            iRetVal = -1
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Error...")
        Catch ex As Exception
            iRetVal = -1
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, "Error...")

        Finally
            oDt = Nothing
            oRdr.Close()
            oRdr = Nothing
            oComm.Dispose()
            oComm = Nothing
            If oConn.State = ConnectionState.Open Then oConn.Close()
            oConn = Nothing
        End Try

        Return iRetVal
    End Function

    Public Property UserName() As String Implements IMyApp.UserName
        Get
            Return sUserName
        End Get
        Set(ByVal value As String)
            sUserName = value
        End Set
    End Property

    Protected Overrides Sub Finalize()
        MyBase.Finalize()
    End Sub

End Class

STEP 2)
Now, we need to declare our class as a global variable. Why? To make it "visible[^]" in all forms (we need a module).
=== module ===

Module MainMod
    'this is a place where you can store global variables

    'take a look into the procedure: MainFrm.New()
    Public oMyApp As IMyApp = Nothing

End Module

STEP 3
Time for Login form
=== login form class ===

Public Class LoginFrm

    Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
        Dim iCount As Integer = 0
        If Me.UsernameTextBox.Text.Length = 0 Or _
            Me.PasswordTextBox.Text.Length = 0 Then
            MsgBox("You need to fill Login and Password", MsgBoxStyle.Information, "Error")
            Exit Sub
        End If

        iCount = MainMod.oMyApp.CheckUser(Me.UsernameTextBox.Text, Me.PasswordTextBox.Text)
        Select Case iCount = 1
            Case 0
                'unknown user
                Me.OK.DialogResult = Windows.Forms.DialogResult.Abort
            Case 1
                'OK
                Me.OK.DialogResult = Windows.Forms.DialogResult.OK
            Case Else
                'more than one user???
                Me.OK.DialogResult = Windows.Forms.DialogResult.Cancel
        End Select

        Me.Close()
    End Sub

    Private Sub Cancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cancel.Click
        Me.Close()
    End Sub

    Private Sub LoginFrm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.UsernameTextBox.Text = Environ("username")
    End Sub
End Class

STEP 4
=== Main form class ===

Public Class MainFrm

    Public Sub New()
        Dim dlgRes As DialogResult = Windows.Forms.DialogResult.OK
        ' This call is required by the Windows Form Designer.
        InitializeComponent()
        ' Add any initialization after the InitializeComponent() call.

        'initiate our class through an interface, take a look into MainMod.vb
        oMyApp = New TMyApp
        'call LoginFrm in a loop 
        Do
            dlgRes = LoginFrm.ShowDialog()
            'if user cancel login, skip initialization of apllication
            If dlgRes = Windows.Forms.DialogResult.Cancel Then Exit Sub
            'welcome ;)
            If dlgRes = Windows.Forms.DialogResult.OK And oMyApp.UserName <> String.Empty Then Exit Do
            'unknown user - take a look into LoginFrm.vb
        Loop Until dlgRes = Windows.Forms.DialogResult.Abort

        'Simple initialization :)
        Me.LblInfo.Text = "Welcome " & oMyApp.UserName & "!"

    End Sub

    Protected Overrides Sub Finalize()
        oMyApp = Nothing
        MyBase.Finalize()
    End Sub

End Class

Maybe this is not optimal coding (especially the part of login), so i say: sorry.
The most important idea was: to show a simple, working example.

I hope it will be helpful ;)

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