WebClient.DownloadFile 转换为文件 VB.NET

Question

有谁知道如何将 Webclient.DowloadFile 解析为 VB.Net 中的文件？我目前正在使用以下代码，但我不断收到错误消息： (BC30491) 表达式不产生值。 (BC30311)类型值无法转换为文件

Private Function DepartmentDataDownloader() As String
    Dim webClient As New System.Net.WebClient
    'I get here the error BC30491
    Dim result As File = webClient.DownloadFile("https://intern.hethoutsemeer.nl/index2.php?option=com_webservices&controller=csv&method=hours.board.fetch&key=F2mKaXYGzbjMA4V&element=departments", "intern.hethoutsemeer.nl.1505213278-Departments.csv")

    If webClient IsNot Nothing Then
        'and here BC30311
        Dim result As File = webClient
        UploaderFromDownload(webClient)
    End If
    Return ""
End Function

Answer 1

DownloadFile method doesn't return a value, because DownloadFile is a Sub. This is the reason why you get the BC30491 错误。第二个参数指定本地文件的路径（以及下载的结果）。

因此您可以尝试以下操作：

Dim webClient As New System.Net.WebClient

'after this the file specified on second parameter should exists.
webClient.DownloadFile("https://intern.hethoutsemeer.nl/index2.php?option=com_webservices&controller=csv&method=hours.board.fetch&key=F2mKaXYGzbjMA4V&element=departments", "intern.hethoutsemeer.nl.1505213278-Departments.csv")

If webClient IsNot Nothing Then

    'do something with the downloaded file (File.OpenRead(), File.*).
    'Dim result As File
    UploaderFromDownload(webClient)
End If

您还尝试将 WebClient 值分配给 File 变量。这是不可能的，因此您会收到 BC30311 错误。

Hint: You can't create an instance of the File class. The File class provides static methods for the creation, copying, deletion, moving, and opening of a single file, and aids in the creation of FileStream objects.
source: https://docs.microsoft.com/en-us/dotnet/api/system.io.file

WebClient.DownloadFile 转换为文件 VB.NET

WebClient.DownloadFile convert to File VB.NET

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