我正在为使用 VB 创建的程序开发登录系统。目前系统存在两个问题：第一个是即使用户已经创建了账户，但在程序启动时用户名和密码文件似乎被擦除了；其次，当我尝试登录时，它会引发此错误：
“在 mscorlib.dll 中发生了“System.IO.IOException”类型的未处理异常
附加信息：该进程无法访问文件 'J:\Computing Coursework\real project\KES\Resources\username.txt'，因为它正被另一个进程使用。”
系统代码如下：
Imports System.IO
Public Class Login
Private Sub Login_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private usernameWriter As New StreamWriter("J:\Computing Coursework\real project\KES\Resources\username.txt") 'Creates the stream for writing the username to file
Private passwordWriter As New StreamWriter("J:\Computing Coursework\real project\KES\Resources\password.txt") 'Creates the stream for writing the password to file
Dim currentLogin As String 'Allows the program to recognise which user is logged in currently
Private Sub btn_CreateAccount_Click(sender As Object, e As EventArgs) Handles btn_CreateAccount.Click
usernameWriter.WriteLine(txtbox_UsernameCreate.Text) 'Writes the username to the username file.
passwordWriter.WriteLine(txtbox_PasswordCreate.Text) 'Writes the password to the password file.
usernameWriter.Close() 'Closes the username file after writing to it so that changes are saved to the file.
passwordWriter.Close() 'Closes the password file for the same reason as the username file above.
currentLogin = txtbox_UsernameCreate.Text
Dim statsFile As New StreamWriter("J:\Computing Coursework\real project\KES\Resources\" + currentLogin + ".txt")
Tokyo.Show() 'Tokyo is the name for the main menu
Me.Hide() 'As Login is the startup form for this solution, it is hidden instead of closed so that the program will not terminate when the login screen dissapears.
End Sub
Private Sub btn_Login_Click(sender As Object, e As EventArgs) Handles btn_Login.Click
Dim usernameReader As New StreamReader("J:\Computing Coursework\real project\KES\Resources\username.txt") 'Sets the location for the username to be found in
Dim passwordReader As New StreamReader("J:\Computing Coursework\real project\KES\Resources\password.txt") 'Sets the location for the password to be found in
Dim n As Integer
Dim i As Integer
While n < 101 'Checks the first 100 lines for the username
If txtbox_UsernameCreate.Text = usernameReader.ReadLine Then 'If the username is found close the usernameReader and move on to the password
usernameReader.Close()
While i < 101 'checks the first 100 password entries
If txtboxPassword.Text = passwordReader.ReadLine Then 'If the password is found then close the passwordReader, set the login ID and then open the main menu
passwordReader.Close()
currentLogin = txtbox_UserName.Text
Me.Hide()
Tokyo.Show()
Else
i += 1 'otherwise it increments the count so that the next line can be read
End If
MsgBox("No valid password") 'If the first 100 lines have been checked and there is no password then this returns the msgbox
End While
Else
n += 1 'otherwise it increments the count so that the next line can be read
End If
MsgBox("No valid username") 'If the first 100 lines have been checked and there is no username then this returns the msgbox
End While
End Sub
End Class
对上述问题的任何帮助将是一个相当大的帮助。