如何验证用户名和密码以登录，然后根据可以触发的不同事件检查usertype？
例如，admin具有某些权限，普通用户具有不同的权限。
公共课程登录
Dim con As New OleDb.OleDbConnection
'new connection to database
Dim dbprovider As String
'to gets the probider name
Dim dbsource As String
'to gets the database provider name
Dim ds As New DataSet
'dataset to table
Dim da As OleDb.OleDbDataAdapter
'databaseAdapter to dataset and database
Dim sql As String
'sql command
Dim usrname1, pswd1, usrtype As String
Dim maxrows, incdec As Integer
'string variables
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
'validation of username and password
If txtb_uname.Text = usrname1 And txtb_pwd.Text = pswd1 Then
If usrtype = "admin" Then
Score.Show()
Score.btn_delete.Enabled = False
Score.btn_update.Enabled = False
Score.Button2.Enabled = False
Score.Button1.Enabled = False
'username and password correct go to the netx page
ElseIf txtb_uname.Text = usrname1 And txtb_pwd.Text = "" Then
MsgBox("Enter Password")
'blank password control
ElseIf txtb_uname.Text = "" And txtb_pwd.Text = pswd1 Then
MsgBox("Enter Username")
'blank username control
ElseIf txtb_uname.Text = usrname1 And txtb_pwd.Text <> pswd1 Then
MsgBox("Invalid Password")
'incorrect pasword
ElseIf txtb_uname.Text <> usrname1 And txtb_pwd.Text = pswd1 Then
MsgBox("Invalid Username")
'incorrect username
ElseIf txtb_uname.Text = "" And txtb_pwd.Text = "" Then
MsgBox("enter Username")
'blank username and password
Else
MsgBox("invalid usertype")
End If
Else
MsgBox("Invalid Username & or Password")
'incorrect username and password
End If
End Sub
答案 0 :(得分：0)
让我们假设您的数据库有一个包含用户名，密码和布尔值的表，其名称类似于isAdmin，可以设置为true或false，具体取决于用户权限。
现在您必须使用数据库连接来验证用户名和密码。这是一个小例子：
Public Shared Function Login(ByVal Name As String, ByVal Password As String) As Boolean
Shared OleDbConString As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & My.Settings.Netzwerkpfad & ";" 'you'll have to enter your own provider etc. I just copied it from another project
Shared con As OleDbConnection = New OleDbConnection(OleDbConString) 'establish the connection
Shared cmd As New OleDbCommand 'your sql statement
Shared reader As OleDbDataReader 'Saving the data you'll get
Dim Checkpassword String = "" 'The string where you'll put the password you get from the databse
Dim isAdmin as boolean = False
Try
cmd.Connection = con
cmd.CommandText = "SELECT Password, isAdmin FROM tbl_User WHERE Name = '" & Name & "';" 'tbl_User is just the table name, this may be different in your DB
con.Open() 'opens the database connection
reader = cmd.ExecuteReader 'executes your command
Do While reader.Read
Checkpassword = reader("Password") 'reader("Password") returns the column "Password" in your databse
isAdmin = reader("isAdmin") 'Returns true or false depending on the users rights
Loop
If Password.Equals(Checkpassword ) Then 'Checks if the entered password is correct
If isAdmin = True Then 'Check if Admin and based on the outcome call the functions or save the outcome into global variables
Else
End If
Else
End If
Catch ex As Exception
MessageBox.Show(ex.Message, "Error while trying to log in", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return Nothing
Finally
con.Close()
End Try
End Function
答案 1 :(得分：0)
公共类frmAdminLoginpage
Dim ErrorCount As Integer
Private Sub frmAdminLoginpage_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ErrorCount = 0
End Sub
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
MessageBox.Show("Are you sure you want to Exit?", "Exit", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation)
Me.Close()
End Sub
Private Sub lblCreateAccount_LinkClicked(sender As Object, e As LinkLabelLinkClickedEventArgs) Handles lblCreateAccount.LinkClicked
frmRegister.Show()
Me.Hide()
End Sub
Private Sub lblForgotPassword_LinkClicked(sender As Object, e As LinkLabelLinkClickedEventArgs) Handles lblForgotPassword.LinkClicked
frmForgotPassword.Show()
Me.Hide()
End Sub
Sub ClearControls()
txtLoginID.Text = ""
txtLoginPassword.Text = ""
txtLoginID.Focus()
End Sub
Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
'Clear text
ClearControls()
End Sub
Protected Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
Dim strConnectionString As String
Dim sqlCnn As SqlConnection
Dim sqlCmd As SqlCommand
Dim adapter As New SqlDataAdapter
Dim ds As New DataSet
Dim strSQL As String
' Check if ID or password is empty
If txtLoginPassword.Text = "" Or txtLoginID.Text = "" Then
MessageBox.Show("Please Enter your ID and Password.", "Authentication Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
' Both fields was supply
' Check if user exist in database
' Connect to Database
strConnectionString = "Data Source=LENOVO-PC; Initial Catalog=VB; Integrated Security=True"
Try
'Database records will verify the Staff ID, password and position from the Staff Database
strSQL = "Select * FROM Staff WHERE StaffID='" & txtLoginID.Text & "'And Password = '" & txtLoginPassword.Text & "'And Position='Administrator'"
'strSQL = "Select * FROM Staff WHERE Position='Administrator'"
sqlCnn = New SqlConnection(strConnectionString)
'Open Database Connection
sqlCnn.Open()
sqlCmd = New SqlCommand(strSQL, sqlCnn)
Dim sqlReader As SqlDataReader = sqlCmd.ExecuteReader
If sqlReader.Read() Then
frmSales_Admin.Show()
Me.Hide()
Else
' If user enter wrong ID and password
' Throw an error message
MessageBox.Show("Incorrect User ID and Password..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
ErrorCount = ErrorCount + 1
'Clear all fields
txtLoginID.Text = ""
txtLoginPassword.Text = ""
'Focus on login ID field
txtLoginID.Focus()
'If login was not successful at the first time, the user will only have two more Login attempts left
If (ErrorCount = 1) Then
lblNotify.Text() = "You have 2 login attempts left"
'If login was not successful for the second time, the user will only have one more Login attempts left
ElseIf (ErrorCount = 2) Then
lblNotify.Text() = "You have 1 login attempt left"
'If login was not successful for the third time, the user will not have anymore attempts left
ElseIf (ErrorCount = 3) Then
MessageBox.Show(" You have exceeded the maximum login attempts. System is now exiting. ", " Error! ", MessageBoxButtons.OK, MessageBoxIcon.Error)
'The system will then exit after the message box is closed
Application.Exit()
End If
End If
Catch ex As Exception
MessageBox.Show("Failed to connect to Database.", "Database Connection Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
End If
End Sub
Private Sub chkShowPassword_CheckedChanged(sender As Object, e As EventArgs) Handles chkShowPassword.CheckedChanged
'To Make Password Visible
If chkShowPassword.Checked Then
txtLoginPassword.PasswordChar = ""
ElseIf chkShowPassword.Checked = False Then 'To make password not visible
txtLoginPassword.PasswordChar = "*"
End If
End Sub
Private Sub txtLoginID_DoubleClick(sender As Object, e As EventArgs) Handles txtLoginID.DoubleClick
txtLoginID.Clear()
txtLoginID.Focus()
End Sub
Private Sub btnBack_Click(sender As Object, e As EventArgs) Handles btnBack.Click
'To go back to the main page of the app
frmSmartBookStore.Show()
Me.Hide()
End Sub
Private Sub txtLoginPassword_KeyDown(sender As Object, e As KeyEventArgs) Handles txtLoginPassword.KeyDown
Dim strConnectionString As String
Dim sqlCnn As SqlConnection
Dim sqlCmd As SqlCommand
Dim adapter As New SqlDataAdapter
Dim ds As New DataSet
Dim strSQL As String
'If user press enter key on password textbox
If e.KeyCode = Keys.Enter Then
If txtLoginPassword.Text = "" Or txtLoginID.Text = "" Then
MessageBox.Show("Please Enter your ID and Password.", "Authentication Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
' Both fields was supply
' Check if user exist in database
' Connect to Database
strConnectionString = "Data Source=LENOVO-PC; Initial Catalog=VB; Integrated Security=True"
Try
strSQL = "Select * FROM Staff WHERE StaffID='" & txtLoginID.Text & "'And Password = '" & txtLoginPassword.Text & "'And Position='Administrator'"
'strSQL = "Select * FROM Staff WHERE Position='Administrator'"
sqlCnn = New SqlConnection(strConnectionString)
'Open Database Connection
sqlCnn.Open()
sqlCmd = New SqlCommand(strSQL, sqlCnn)
Dim sqlReader As SqlDataReader = sqlCmd.ExecuteReader
If sqlReader.Read() Then
frmSales_Admin.Show()
Me.Hide()
Else
' If user enter wrong username and password combination
' Throw an error message
MessageBox.Show("Incorrect User ID or Password..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
ErrorCount = ErrorCount + 1
'Clear all fields
txtLoginID.Text = ""
txtLoginPassword.Text = ""
'Focus on login ID field
txtLoginID.Focus()
'If login was not successful at the first time, the user will only have two more Login attempts left
If (ErrorCount = 1) Then
lblNotify.Text() = "You have 2 login attempts left"
'If login was not successful for the second time, the user will only have one more Login attempts left
ElseIf (ErrorCount = 2) Then
lblNotify.Text() = "You have 1 login attempt left"
'If login was not successful for the third time, the user will not have anymore attempts left
ElseIf (ErrorCount = 3) Then
MessageBox.Show(" You have exceeded the maximum login attempts. System is now exiting. ", " Error! ", MessageBoxButtons.OK, MessageBoxIcon.Error)
'The system will then exit after the message box is closed
Application.Exit()
End If
End If
Catch ex As Exception
MessageBox.Show("Failed to connect to Database.", "Database Connection Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try
End If
End If
End Sub
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