Question

我在YouTube上找到了一个代码，当我在visual basic上使用它并调试它并查找图片时，但是当我想保存它们时，软件会给我这条消息here。

Private Sub btnSaveImages_Click(ByVal sender As  _
    System.Object, ByVal e As System.EventArgs) Handles _
    btnSaveImages.Click
    Dim dir_name As String = txtDirectory.Text
    If Not dir_name.EndsWith("\") Then dir_name &= "\"

    For Each pic As PictureBox In flpPictures.Controls
        Dim bm As Bitmap = pic.Image
        Dim filename As String = pic.Tag
        filename = _
            filename.Substring(filename.LastIndexOf("/") + _
            1)
        Dim ext As String = _
            filename.Substring(filename.LastIndexOf("."))
        Dim full_name As String = dir_name & filename

        Select Case ext
            Case ".bmp"
                bm.Save(full_name, Imaging.ImageFormat.Bmp)
            Case ".gif"
                bm.Save(full_name, Imaging.ImageFormat.Gif)
            Case ".jpg", "jpeg"
                bm.Save(full_name, Imaging.ImageFormat.Jpeg)
            Case ".png"
                bm.Save(full_name, Imaging.ImageFormat.Png)
            Case ".tiff"
                bm.Save(full_name, Imaging.ImageFormat.Tiff)
            Case Else
                MessageBox.Show( _
                    "Unknown file type " & ext & _
                    " in file " & filename, _
                    "Unknown File Type", _
                    MessageBoxButtons.OK, _
                    MessageBoxIcon.Error)
        End Select
    Next pic

    Beep()
End Sub

Answer 1

问题在于LastIndexOf没有找到。在你的文件名中。然后将-1传递给SubString，抛出您正在看到的错误。

不使用自己编写文件解析，而是使用System.Io.Path的方法，例如

    System.IO.Path.GetDirectoryName(filename)
    System.IO.Path.GetFileName(filename)
    System.IO.Path.GetFileNameWithoutExtension(filename)

Private Sub btnSaveImages_Click(ByVal sender As  _
    System.Object, ByVal e As System.EventArgs) Handles _
    btnSaveImages.Click

    For Each pic As PictureBox In flpPictures.Controls
        Dim bm As Bitmap = pic.Image
        Dim path As String = pic.Tag
        Dim filename = IO.Path.GetFileName(path)
        Dim ext = IO.Path.GetExtension(path)
        Dim full_name = IO.Path.Combine(txtDirectory.txt, filename)

...

使用VB.NET从网站上删除图片时保存图片

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