VB中的登录系统问题 [英] Issue with login system in VB

问题描述

大家好，



i我的登录系统有问题，并寻求一些极客帮助:)

使用第一个用户时（管理员）系统做了它需要做的事情。

但是当我尝试使用其他用户登录时它不会工作。

我收到我的错误用户名和密码未知



当我从代码中删除以下行时，我可以与所有其他用户一起登录



ElseIf（currentUser<>用户名AndAlso currentPassword<>密码）然后

MessageBox.Show（用户名和密码未知，错误，MessageBoxButtons.OK，MessageBoxIcon.Error ）

返回错误

Hi all,

i have an issue with my loginsystem and seek for some geek help :)
When using the first made user (admin) the system does what it needs to do.
But when i try to login with a different user it wont work.
And i get my error "username and password unknown"

When i remove following lines from the code i can login with all other users

ElseIf (currentUser <> username AndAlso currentPassword <> password) Then
MessageBox.Show("Username and password unknown", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return False

Public Function Login(ByVal username As String, ByVal password As String)
        Dim usersDatasSet As New DataSet()
        usersDataAdapter.FillSchema(usersDatasSet, SchemaType.Source, "Users")
        usersDataAdapter.Fill(usersDatasSet, "Users")
        Dim table As DataTable = usersDatasSet.Tables("Users")

        For i As Integer = 0 To table.Rows.Count - 1
            Dim currentUser As String = table.Rows(i)("Username").ToString().Trim()
            Dim currentPassword As String = table.Rows(i)("Password").ToString().Trim()


            'Check input

            If (currentUser <> username And currentPassword = password) Then
                MessageBox.Show("Unknown user", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                Return False

            ElseIf (currentUser = username And currentPassword <> password) Then
                MessageBox.Show("Wrong password", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                Return False


            ElseIf (currentUser <> username AndAlso currentPassword <> password) Then
                MessageBox.Show("Username and  password unknown", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                Return False

            ElseIf (currentUser = username AndAlso currentPassword = password) Then
                usersDatasSet.Dispose()
                Connection.Close()
                Return True
            End If

        Next
        usersDatasSet.Dispose()
        Connection.Close()
        Return False
    End Function

感谢您在此问题上的任何帮助

Thanks for any help in this issue

推荐答案

您好b $ b

首先您需要移动

Hi
First you need to move the

Return

循环语句，因为在检查第一行时条件检查可能会失败。但是第二行中可能存在正确的用户名和密码组合。使用标志来设置要返回的值，并在循环结束后检查该标志。



以下是示例更改的代码：

statements out of the loop as condition check may fail when checking even the first row. But the correct user name and password combination may be present in the second row. Use flags to set the value to be returned and check that flag once the loop is over.

Here is the sample changed code:

Public Function Login(ByVal username As String, ByVal password As String)
        Dim usersDatasSet As New DataSet()
        usersDataAdapter.FillSchema(usersDatasSet, SchemaType.Source, "Users")
        usersDataAdapter.Fill(usersDatasSet, "Users")
        Dim table As DataTable = usersDatasSet.Tables("Users")

        Dim currentUser As String = String.Empty
        Dim currentPassword As String = String.Empty
        Dim IsValid As Boolean = False

        For i As Integer = 0 To table.Rows.Count - 1
            currentUser = table.Rows(i)("Username").ToString().Trim()
            currentPassword = table.Rows(i)("Password").ToString().Trim()

            'Check input
            If (currentUser <> username And currentPassword = password) Then
                IsValid = False
                ' MessageBox.Show("Unknown user", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                'Return False

            ElseIf (currentUser = username And currentPassword <> password) Then
                IsValid = False
                'MessageBox.Show("Wrong password", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                'Return False
            ElseIf (currentUser <> username AndAlso currentPassword <> password) Then
                IsValid = False
                'MessageBox.Show("Username and  password unknown", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
                'Return False
            ElseIf (currentUser = username AndAlso currentPassword = password) Then
                IsValid = True
                usersDatasSet.Dispose()
                Connection.Close()
                'Return True
            End If
        Next

        ' Check if Validation succeeded
        If IsValid = False Then
            'Show Message
            Return False
        Else
            Return True
        End If
        usersDatasSet.Dispose()
        Connection.Close()
        Return False
    End Function

谢谢你的回复。我会尝试这个

Thanks for your reply. I will try this

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