检查文件是否有多个扩展名？

Question

I'm wondering if it is possible to check if a file matches a list of set extention. at the moment i have a working code that only checks a file to see if it has a .txt .jpg or .mp3

Example

If (Path.GetExtension(f).ToLower() = ".txt") Then
                ' It's a .txt file
                '         MsgBox("I am a Txt Document")
                b.Image = My.Resources.Text_Img

            ElseIf (Path.GetExtension(f).ToLower() = ".jpg") Then
                b.Image = My.Resources.Img_Img
            Else
                b.Image = My.Resources.Folder_Img
            End If

This code simply set the image for the Shortcut. I want to be able to check if a file matches more than a txt but a .doc .log then all video types mp4 avi mpg. then all Audio types mp3 ogg flacc acc

Tried, But Failed

ElseIf (Path.GetExtension(f).ToLower() = ".jpg"  & ".png" & ".jpeg" & ".tiff") Then
    b.Image = My.Resources.Img_Img
End If

is this possible don't want to add all 100+ extension to each have their own If Statements. Thank you in advanced. -Dan

Answer 1

If you want to avoid the dictionary route (for no real good reason, other than this being an alternative method), you can use an in-line array to check for each group of extensions.

Dim extension = Path.GetExtension(f).ToLower

If {".txt"}.Contains(extension) Then
    b.Image = My.Resources.Text_Img
ElseIf {".jpg", ".png", ".tif"}.Contains(extension) Then
    b.Image = My.Resources.Img_Img
Else
    b.Image = My.Resources.Folder_Img
End If

I'm sure there are perfectly valid and aesthetically pleasing methods using RegEx and all sorts of LINQ or other weird ways of doing it!

Answer 2

Rather than an If you could look up the code from a dictionary of values. Declare the dictionary as:

Dim dictionary As New Dictionary(Of String, TheResourceType)
dictionary.Add(".txt", My.Resources.Text_Img)
dictionary.Add(".jpg", My.Resources.Img_Img)
dictionary.Add(".png", My.Resources.Img_Img)
dictionary.Add(".jpeg", My.Resources.Img_Img)
dictionary.Add(".tiff", My.Resources.Img_Img)

The question is not clear about the type of b.Image or the My.Resources... values, so change TheResourceType as needed.

Access the values with code like:

Dim ext As Path.GetExtension(f).ToLower()
If dictionary.ContainsKey(ext) Then
    b.Image = dictionary.Item(ext)
Else
    b.Image = My.Resources.Folder_Img
End If

Answer 3

Do something like that:

Dim extension As String = Path.GetExtension(f).ToLower()

If extension.Equals("txt") Then
    b.Image = My.Resources.Text_Img
ElseIf extension.Equals("jpg") OrElse extension.Equals("png") OrElse extension.Equals("tif") Then
    b.Image = My.Resources.Img_Img
Else
    b.Image = My.Resources.Folder_Img
End If

In above code Path.GetExtension() method is called only once, instead of every time the extension is checked. Second, it uses string build-in Equals() method to check extensions. Third, syntax of the check against multiple extensions is fixed - look at the second condition regarding the image files - it is slightly different than yours.

Answer 4

You may have already considered this, but another option (if this is a common need) would be to create a database table of common extensions and then write a function to query that table, passing in Path.GetExtension as a parameter.

An exhaustive list of extensions for such database table can be found here: http://www.freeformatter.com/mime-types-list.html