Question

我有一个vb.net表单程序，通过与数据库的oledb连接进行链接。该数据库包含一个名为tbl_user的登录表。在程序中，用户输入他们的用户名和密码，并与表值

进行比较

Dim sql As String = "SELECT * FROM tbl_user WHERE username='" & txtUsername.Text & "' AND password = '" & txtPassword.Text & "' "
            Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql)
            sqlCom.Connection = conn
            conn.Open()
            Dim sqlRead As System.Data.OleDb.OleDbDataReader = sqlCom.ExecuteReader()

但是我也希望在它检测到的行上传递另一段数据，这一列称为accesslvl。所以我试图通过它然后将它与语句进行比较。我无法弄清楚如何选择并返回accesslvl值。

尝试的事情：

Dim sql As String = "SELECT * FROM tbl_user WHERE username='" & txtUsername.Text & "' AND password = '" & txtPassword.Text & "' "
        Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql)
        Dim accesslvl As String = "SELECT accesslvl FROM tbl_user WHERE username='" & txtUsername.Text & "' AND password = '" & txtPassword.Text & "' "
        Dim accesslvlCom As New System.Data.OleDb.OleDbCommand(accesslvl)
        Dim accesslvlInt As Integer
        Open Database Connection
        sqlCom.Connection = conn
        conn.Open()
        accesslvlCom = accesslvlInt

sql字符串的变体，例如

- "SELECT username,password,accesslvl FROM tbl_user WHERE username='" & txtUsername.Text & "' AND password = '" & txtPassword.Text & "' "

accesslvl的值都是0到3之间的整数。这一点是这样的，当返回accesslvl时，它将加载正确的ui。

Answer 1

这就是我这样做的方式（希望它有所帮助！）：

Imports System.Data.OleDb
Public Class Login
        Dim cn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Application.StartupPath & "\database.mdb;")
        Dim cm As New OleDbCommand
        Dim da As New OleDbDataAdapter
        Dim ds As New DataSet
        Dim username, password As String
        Dim accesslvl As Integer
    Private Sub button1_click(sender as object, e as EventArgs) Handles Button1.Click
        'Opening the connection'
        cn.Open()
        cm.Connection = cn
        cm.CommandType = CommandType.Text
        cm.CommandText = "Select * from tbl_user Where username='" & txtUsername.text & "' and Password='" & txtPassword.text & "'"
        'Execute command'
        cm.ExecuteNonQuery()
        'Close the connection'
        cn.Close()
        'data adapter is an oledb object which collects data from selected command'
        da.SelectCommand = cm
        'Then it fills the data set with that data'
        da.Fill(ds)
        'If there are no data(or no rows) Then'
        If ds.Tables(0).Rows.Count = 0 Then
            MessageBox.Show("Wrong username/password error goes here", "Error", MessageBoxButtons.OK)
            Exit Sub
        End If 
        'However if there is the string username will get the value of the Username column in the row 0 (the only row if there are no duplicates)'
        username = ds.Tables(0).Rows(0).Item("Username")
        'same with this one'
        password = ds.Tables(0).Rows(0).Item("Password")
        'so now beacuse the access is no case sensitive we must check the password. If its ok we are giving the accesslvl value to the accesslvl integer'
        If txtUsername.Text = username And txtPassword.Text = password Then
        accesslvl = CInt(ds.Tables(0).Rows(0).Item("accesslvl"))
        MessageBox.Show("successful login message goes here", "Login", MessageBoxButtons.OK)
        End If
    End Sub
End Class

将数据库信息传递到已选择的行上的Vb.net

1 个答案: