BC30451 'VARIABLE' 未声明。由于其保护级别，它可能无法访问答案

【问题标题】：BC30451 'VARIABLE' is not declared. It may be inaccessible due to its protection levelBC30451 'VARIABLE' 未声明。由于其保护级别，它可能无法访问
【发布时间】：2016-11-06 01:41:33
【问题描述】：

我似乎对下面的代码有错误。

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Me.CenterToScreen()


    If My.Computer.FileSystem.FileExists("bin\php\php.exe") Then
        Dim PHPRC As String = ""
        Dim PHP_BINARY As String = "bin\php\php.exe"
    Else
        Dim PHP_BINARY As String = "php"
    End If

    If My.Computer.FileSystem.FileExists("PocketMine-MP.phar") Then
        Dim POCKETMINE_FILE As String = "PocketMine-MP.phar"
    Else
        If My.Computer.FileSystem.FileExists("src\pocketmine\PocketMine.php") Then
            Dim POCKETMINE_FILE As String = "src\pocketmine\PocketMine.php"
        Else
            MsgBox("Couldn't find a valid PocketMine-MP installation", MsgBoxStyle.Exclamation, "PocketMine-MP")
        End If

    End If

    Process.Start("C:\Users\Damian\Desktop\Games\Pocketmine\Installer\PocketMine-MP\bin\mintty.exe", "-o Columns=88 -o Rows=32 -o AllowBlinking=0 -o FontQuality=3 -o Font='DejaVu Sans Mono' -o FontHeight=10 -o CursorType=0 -o CursorBlinks=1 -h error -t 'PocketMine-MP' -i bin/pocketmine.ico -w max" & PHP_BINARY & "" & POCKETMINE_FILE & "" & "--enable-ansi")

End Sub

我不断收到此错误

BC30451 'PHP_BINARY' 未声明。由于其保护级别，它可能无法访问。

BC30451 'POCKETMINE_FILE' 未声明。由于其保护级别，它可能无法访问。

我做错了什么？

（仅供参考，出于测试原因，它在 Form1_Load 中。）

【问题讨论】：

标签： vb.net windows mintty

【解决方案1】：

您正在使 if 语句中的两个变量变暗，因此一旦您点击“end if”，您的变量就会消失或“超出范围”。您绝对应该对variable scope 进行一些研究...要在您的代码中解决此问题，首先在子代码内部但在 if 语句之外声明字符串。然后只需使用 if 语句来更改变量的内容；这样，当您的流程调用出现时，变量不会超出范围：

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Me.CenterToScreen()

    Dim PHP_BINARY As String = Nothing
    Dim POCKETMINE_FILE As String = Nothing

    If My.Computer.FileSystem.FileExists("bin\php\php.exe") Then
        PHP_BINARY = "bin\php\php.exe"
    Else
        PHP_BINARY = "php"
    End If

    If My.Computer.FileSystem.FileExists("PocketMine-MP.phar") Then
        POCKETMINE_FILE = "PocketMine-MP.phar"
    Else
        If My.Computer.FileSystem.FileExists("src\pocketmine\PocketMine.php") Then
            POCKETMINE_FILE = "src\pocketmine\PocketMine.php"
        Else
            MsgBox("Couldn't find a valid PocketMine-MP installation", MsgBoxStyle.Exclamation, "PocketMine-MP")
        End If

    End If

    Process.Start("C:\Users\Damian\Desktop\Games\Pocketmine\Installer\PocketMine-MP\bin\mintty.exe", "-o Columns=88 -o Rows=32 -o AllowBlinking=0 -o FontQuality=3 -o Font='DejaVu Sans Mono' -o FontHeight=10 -o CursorType=0 -o CursorBlinks=1 -h error -t 'PocketMine-MP' -i bin/pocketmine.ico -w max" & PHP_BINARY & "" & POCKETMINE_FILE & "" & "--enable-ansi")

End Sub

【讨论】：