以编程方式检测计算机上的JDK安装

Question

这是我在一台机器上检测JDK安装的函数的代码。执行时的代码给出了处理的异常： -

第164号线是： - If ndpKey Is Nothing AndAlso ndpKey.GetValue("CurrentVersion") Is Nothing Then

Private Function HAS_JDK() As Boolean
    Try
        Const subkeyjava As String = "SOFTWARE\JavaSoft\Java Runtime Environment"

        Using ndpKey As RegistryKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32).OpenSubKey(subkeyjava)
            If ndpKey Is Nothing AndAlso ndpKey.GetValue("CurrentVersion") Is Nothing Then
                Close()
                Return False
            Else
                Return True
            End If
        End Using

    Catch e As NullReferenceException
        MessageBox.Show("System Error Occured While Checking JDK !! ", "BLA BLA BLA - Error Occured !!")
        MessageBox.Show(e.ToString())
        Close()
        Return -1
    End Try
End Function

Answer 1

你的逻辑有点不正确。我认为你所追求的是OrElse：

If ndpKey Is Nothing OrElse ndpKey.GetValue("CurrentVersion") Is Nothing Then

这检查ndpKey或ndpKey.GetValue("CurrentVersion")是否为空。如果第一次检查成功，它将不会继续第二次，因此没有例外。