读取文本文件以查找活动产品密钥

Question

我做了一个产品密钥系统，有一个文本框，当我点击激活它读取具有活动产品密钥的文本文件，并检查以确保文本框文本与文本文件中的活动代码之一相同。但是，如果我输入一个无效的代码，它就会死机!也许是错误的代码?下面是我的代码:

    Dim code As String
    code = TextBox1.Text
    Try
        Dim sr As IO.StreamReader = New IO.StreamReader("C:UsersChristest.txt")
        Dim line As String
        Do
        line = sr.ReadLine
        Loop Until line = code
        sr.Close()
        my.settings.registered=True
        MsgBox("Your code is valid")
    Catch ex As Exception
        MsgBox("You have entered an invalid code, please try again", MsgBoxStyle.Critical)

    End Try

Answer 1

您没有检查是否已到达文件的末尾，因此您的应用程序可能会抛出您未捕获的异常。您需要检查是否到达了流的末尾:

Do Until sr.EndOfStream
    ....
Loop

应该修复它

注意:你也应该在你完成后处理你的StreamReader对象。但最好还是把它包装在Using块中，这样你就不用记得去做了!

最好将所有这些都包装成这样的函数:

Private Function IsValidCode(ByVal code As String) As Boolean
    Dim line As String
    Using sr As New StreamReader("yourfile")
        Do Until sr.EndOfStream
            line = sr.ReadLine
            If line = code Then Return True
        Loop
    End Using
    Return False
End Function

Answer 2

试着改变你的循环…

Do
    line = sr.ReadLine
    if line = code then
      '.................
      exit do 
    end if
Loop Until line is Nothing