Question

我创建了一个函数来检查文件＆＃34; test.txt＆＃34;存在：

Public Function CheckIfFileExists(sFileName As String) As Integer

     Dim Location As Windows.Storage.StorageFolder = Windows.ApplicationModel.Package.Current.InstalledLocation
     Dim lstfiles = Location.GetFilesAsync(Search.CommonFileQuery.OrderByName)
     Dim foundfiles = lstfiles.GetResults
     Dim bFound As Integer
     bFound = 0

     If foundfiles IsNot Nothing Then

         For Each sFile In foundfiles
             If sFile.Name = sFileName Then
                 bFound = 1
                 Exit For
             End If
        Next
     End If
     Return bFound

End Function

现在，当我第一次在主函数中调用CheckIfFileExists（FILENAME）时，例如

CheckIfFileExists("test.txt")

，它返回一个＆＃34; System.Runtime.InteropServices.COMException＆＃34;说我在意外的时间调用了这个方法。

Exception thrown: 'System.UnauthorizedAccessException' in mscorlib.ni.dll

是否与我在同步函数中使用异步函数有关？

如果是，我如何修改我的功能以异步工作？

谢谢！

Answer 1

是否与我在同步函数中使用异步函数有关？

是的，您应该始终等待异步GetFilesAsync方法：

Public Async Function CheckIfFileExists(sFileName As String) As Task(Of Integer)

    Dim Location As Windows.Storage.StorageFolder = Windows.ApplicationModel.Package.Current.InstalledLocation
    Dim lstfiles = Await Location.GetFilesAsync(Search.CommonFileQuery.OrderByName)
    Dim foundfiles = lstfiles
    Dim bFound As Integer
    bFound = 0

    If foundfiles IsNot Nothing Then
        For Each sFile In foundfiles
            If sFile.Name = sFileName Then
                bFound = 1
                Exit For
            End If
        Next
    End If
    Return bFound
End Function

CheckIfFileExists方法：

Dim b As Boolean = Await CheckIfFileExists("test.txt")

UWP：检查，创建数据并将其添加到文件

1 个答案: