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

Question

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

我一直收到这个错误

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，它在 Form1_Load 中只是出于测试原因。）

Answer 1

您在 if 语句中使两个变量变暗，所以一旦您点击 "end if"，您的变量就会消失，或者 "out of scope"。你绝对应该对 variable scope 做一些研究......要在你的代码中解决这个问题，首先在 sub 内部但在你的 if 语句之外声明字符串。然后只需使用 if 语句来更改变量所包含的内容；这样，当您的流程调用出现时，变量将不会超出范围：

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

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

BC30451 'VARIABLE' is not declared. It may be inaccessible due to its protection level

vb.net

windows

mintty