を使用するSystem.IO.Directory.Existsと、ディレクトリが見つからなかったことだけが通知されますが、これは、ディレクトリが実際には存在しないか、ユーザーがディレクトリへの十分なアクセス権を持っていないことが原因である可能性があります。
これを解決するために、ディレクトリが存在しない本当の理由を取得できなかった後に二次テストを追加し、これを標準メソッドDirectory.Existsの代わりに使用されるグローバル メソッドにラップしました。Directory.Exists
''' <summary>
''' This method tests to ensure that a directory actually does exist. If it does not, the reason for its
''' absence will attempt to be determined and returned. The standard Directory.Exists does not raise
''' any exceptions, which makes it impossible to determine why the request fails.
''' </summary>
''' <param name="sDirectory"></param>
''' <param name="sError"></param>
''' <param name="fActuallyDoesntExist">This is set to true when an error is not encountered while trying to verify the directory's existence. This means that
''' we have access to the location the directory is supposed to be, but it simply doesn't exist. If this is false and the directory doesn't exist, then
''' this means that an error, such as a security error, was encountered while trying to verify the directory's existence.</param>
Public Function DirectoryExists(ByVal sDirectory As String, ByRef sError As String, Optional ByRef fActuallyDoesntExist As Boolean = False) As Boolean
' Exceptions are partially handled by the caller
If Not IO.Directory.Exists(sDirectory) Then
Try
Dim dtCreated As Date
' Attempt to retrieve the creation time for the directory.
' This will usually throw an exception with the complaint (such as user logon failure)
dtCreated = Directory.GetCreationTime(sDirectory)
' Indicate that the directory really doesn't exist
fActuallyDoesntExist = True
' If an exception does not get thrown, the time that is returned is actually for the parent directory,
' so there is no issue accessing the folder, it just doesn't exist.
sError = "The directory does not exist"
Catch theException As Exception
' Let the caller know the error that was encountered
sError = theException.Message
End Try
Return False
Else
Return True
End If
End Function
