有人可以检查我的VB.net代码吗？问题在下面解释

debugcn 发表于 Dev

本安南

好的，我已经使用访问数据库在VB.net上创建了一个登录系统。我遇到的问题是，某些用户名和密码组合可以正常工作，但是其中一些虽然输入正确，但根本无法正常工作。这是我写的代码...

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    ' Check if username or password is empty
    If textpassword.Text = "" Or textusername.Text = "" Then
        MessageBox.Show("Please complete the required fields..", "Authentication Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
    Else
        ' Both fields were supplied
        ' Check if user exist in database
        ' Connect to DB
        Dim conn As New System.Data.OleDb.OleDbConnection()
        conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\database1.accdb"

        'conn.Open()
        'MsgBox("Susscess")

        Dim sql As String = "SELECT * FROM Accounts WHERE username='" & textusername.Text & "' AND password = '" & textpassword.Text & "'"
        Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql)

        'Open Database Connection
        sqlCom.Connection = conn
        conn.Open()

        Dim sqlRead As System.Data.OleDb.OleDbDataReader = sqlCom.ExecuteReader()

        If sqlRead.Read() Then
            MemberPage.Show()
            Me.Hide()

        Else
            ' If user enter wrong username and password combination
            ' Throw an error message
            MessageBox.Show("Username and Password do not match..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

            'Clear all fields
            textpassword.Text = ""
            textusername.Text = ""

            'Focus on Username field
            textusername.Focus()
        End If 
    End If 
End Sub

硬汉

似乎您在填充完之后检查的条件下发生了一些错误dataReader。IE

If sqlRead.Read() Then

if通过以下代码尝试条件

If Not sqlRead Is Nothing  Then

如果不起作用的话..

我建议您使用DataAdapter并检查它是否返回行。如果行数大于1，则必须显示MemberPage

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click


    If textpassword.Text = "" Or textusername.Text = "" Then
        MessageBox.Show("Please complete the required fields..", "Authentication Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
    Else

        Dim conn As New System.Data.OleDb.OleDbConnection()
        conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\database1.accdb"


        Dim sql As String = "SELECT * FROM Accounts WHERE username='" & textusername.Text & "' AND password = '" & textpassword.Text & "'"
        Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql)

        Dim ds As DataSet

        sqlCom.Connection = conn
        conn.Open()

        'Dim sqlRead As System.Data.OleDb.OleDbDataReader = sqlCom.ExecuteReader()

        Dim da as New OleDbDataAdapter(sqlCom)

        da.Fill(ds)

        If ds.Tables(0).Rows.Count > 1  Then
            MemberPage.Show()
            Me.Hide()

        Else

            MessageBox.Show("Username and Password do not match..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)


            textpassword.Text = ""
            textusername.Text = ""


            textusername.Focus()
        End If 
    End If 
End Sub

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