Question

我无法连接到我的数据库，我收到消息＆＃34;无效的用户或密码＆＃34;即使密码是正确的，我应该做什么任何想法或我的代码错在这里是我的登录表单的代码/

这是我的代码

Imports System.Data.SqlClient

Public Class LoginForm

  Private Sub UsersBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs) Handles UsersBindingNavigatorSaveItem.Click
    Me.Validate()
    Me.UsersBindingSource.EndEdit()
    Me.TableAdapterManager.UpdateAll(Me.DataSet1)
End Sub

Private Sub LoginForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    'TODO: This line of code loads data into the 'DataSet1.users' table. You can move, or remove it, as needed.
    Me.UsersTableAdapter.Fill(Me.DataSet1.users)

End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
  Dim connection As New SqlConnection("Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Database_topdent.mdf;Integrated Security=True")
  Dim command As New SqlCommand("Select * from  users where User = @user and Password = @password ", connection)

  command.Parameters.Add("@user", SqlDbType.VarChar).Value = UserTextBox.Text
  command.Parameters.Add("@password", SqlDbType.VarChar).Value = PasswordTextBox.Text

  Dim adapter As New SqlDataAdapter(command)
  Dim table As New DataTable()
  adapter.Fill(table)

  If table.Rows.Count() <= 0 Then
    MessageBox.Show("username or textbox invalid")
  Else                   
    Form1.Show()
    Me.Hide()
  End If

End If
End Sub
End Class

Answer 1

这太令人困惑了。您需要检查用户名和密码，而不仅仅是计算行数。那个table.rows.count“＆lt; = 0”？对我毫无意义。我可以看到你在哪里，但它错了。而问题本身并不够清楚。但假设这是一个登录表单。试试这个＆gt;

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


            Dim connection As New SqlConnection("Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Database_topdent.mdf;Integrated Security=True")
            Dim command As New SqlCommand("Select * from  [users] where [User] = @1 and [Password] = @2 ", connection)

            connection.Open()

            command.Parameters.AddWithValue("@1", UserTextBox.Text)
            command.Parameters.AddWithValue("@2", PasswordTextBox.Text)

            Using dr As SqlDataReader = command.ExecuteReader

                Dim userFound As Boolean = False

                Dim Name As String = ""

                While dr.Read

                    userFound = True
                    Name = dr("User").ToString

                End While

                If userFound = True Then

                    MsgBox("Yes!")

                ElseIf userFound = False Then

                    MsgBox("nay")


                End If

            End Using

   connection.close()
    End Sub

只需确保您的列设置为vchar即可。我无法测试它，但它应该可以工作。

首先，您需要打开连接。然后，您需要使用阅读器读取数据库中的数据。然后，如果找到用户名和密码，则显示一个msg或任何你想要的内容。我确信有更好的方法可以做到这一点，但在这里，我正在扮演一个快速好的撒玛利亚人。

更新#With权限 1.添加另一个名为“Permissions”的列 2.创建一个模块。

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


            Dim connection As New SqlConnection("Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Database_topdent.mdf;Integrated Security=True")
            Dim command As New SqlCommand("Select * from  [users] where [User] = @1 and [Password] = @2 ", connection)

            connection.Open()

            command.Parameters.AddWithValue("@1", UserTextBox.Text)
            command.Parameters.AddWithValue("@2", PasswordTextBox.Text)

            Using dr As SqlDataReader = command.ExecuteReader

                Dim userFound As Boolean = False



                While dr.Read

                    userFound = True
                    User1 = dr("User").ToString
                    Permissions = dr("Permissions").ToString

                End While

                If userFound = True Then

                    MsgBox("Yes!")

                ElseIf userFound = False Then

                    MsgBox("nay")


                End If

            End Using

   connection.close()
    End Sub

模块

Module Module1

Public User1 As String
Public Permissions As String

End Module

然后在表单中调用内容... 例如，在您的主窗体或任何地方，如果您在加载表单上有2个按钮，则可以执行

If Permissions = "admin" then
Button1.enabled = true
else if Permissions = "user" then
msgbox(fu)
end if

Answer 2

你好这里是我的登录代码，管理员/用户可以使用，但是知道我想在用户登录时做出权限示例，但没有完全访问权限，但管理员是完全访问权限。

以下是“Login_Form”

的所有代码

Imports System.Data.SqlClient
      Module Module1

Public User1 As String
Public Permissions As String


End Module
Public Class LoginForm
    Private Sub UsersBindingNavigatorSaveItem_Click(sender As Object, e As EventArgs) Handles UsersBindingNavigatorSaveItem.Click
        Me.Validate()
        Me.UsersBindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.DataSet1)

End Sub

Private Sub LoginForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    'TODO: This line of code loads data into the 'DataSet1.users' table. You can move, or remove it, as needed.
    Me.UsersTableAdapter.Fill(Me.DataSet1.users)

    If Permissions = "admin" Then
        Button1.Enabled = True
    ElseIf Permissions = "user" Then
        Form1.RaportetToolStripMenuItem.Visible = False
    End If

End Sub

Private Sub Button3_Click(sender As Object, e As EventArgs)

End Sub

Private Sub Button4_Click(sender As Object, e As EventArgs)

End Sub

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



    Dim connection As New SqlConnection("Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Database_topdent.mdf;Integrated Security=True")
    Dim command As New SqlCommand("Select * from  [Table_login] where [Username] = @1 and [Password] = @2 ", connection)

    connection.Open()

    command.Parameters.AddWithValue("@1", UserTextBox.Text)
    command.Parameters.AddWithValue("@2", PasswordTextBox.Text)

    Using dr As SqlDataReader = command.ExecuteReader

        Dim userFound As Boolean = False

        Dim Name As String = ""

        While dr.Read

            userFound = True
            Name = dr("Username").ToString

        End While

        If userFound = True Then

            Form1.Show()


        ElseIf userFound = False Then

            MsgBox("Username or password is wrong!!!!!! ")


        End If

    End Using
    connection.Close()



    If Permissions = "user1" Then
        Form1.RaportetToolStripMenuItem.Visible = False

    End If




End Sub

结束班

登录表单无法连接到数据库

2 个答案: