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• Whenever you work with drives, directories (folders) or files, you should always use a Try...Catch...End Try block because there will always be a risk of unexpected errors.
• Try to avoid using the AllDirectories search option with the Directory.GetFiles command. The GetFiles command will stop with an "access to ... is denied" error message when it encouters a locked file/folder. Combining a Try...Catch...End Try with the TopDirectoryOnly option can allow all "accessible" files/folders to be processed. In many applications, restricted files could be ignored without losing data essetial to the program.
• When creating Try...Catch...End Try blocks, ensure your code does not accidentally override any other aread e.g. Hard disk full. You should also consider the possiblity that an "access is denied" error could relate to an essential file.
• If you allow the user any control over what drive/folder/file is selected, you should also move all drive/folder/file access into a background worker. It is not reasonable to expect a to realise that copying multi-gigabyte files or backing up a primary hard drive could be a slow process.

Some of these examples require the following structure
Public Structure ListFilesError
Dim ListFiles As List(Of String)
Dim ErrorMessage As String>br /> End Structure

 
Private Shared Function ListFiles(folder As String) As ListFilesError
' Top Level Only
' initialise results
Dim ret As ListFilesError
ret.ListFiles = New List(Of String)
ret.ErrorMessage = ""
' get list of files in folder
Try
ret.ListFiles.AddRange(IO.Directory.GetFiles(folder, "*", IO.SearchOption.TopDirectoryOnly))
Catch ex As Exception
ret.ErrorMessage = ex.Message
ret.ListFiles.Clear()
End Try
Return ret
End Function

 
Private Shared Function ListFiles1(folder As String, Optional IgnoreSystemFiles As Boolean = True) As ListFilesError
' Include nested folders
Dim listFoldersTemp As New List(Of String) From {folder}
' initialise results
Dim ret As ListFilesError
ret.ListFiles = New List(Of String)
ret.ErrorMessage = ""
While listFoldersTemp.Count > 1
Try
If (Not IgnoreSystemFiles) OrElse (Not IsSystemFile(listFoldersTemp.Item(0))) Then
listFoldersTemp.AddRange(IO.Directory.GetDirectories(listFoldersTemp.Item(0)))
If IgnoreSystemFiles Then
For Each filename As String In IO.Directory.GetFiles(listFoldersTemp.Item(0))
If Not IsSystemFile(filename) Then
ret.ListFiles.Add(filename)
End If
Next
Else
ret.ListFiles.AddRange(IO.Directory.GetFiles(listFoldersTemp.Item(0)))
End If
End If
listFoldersTemp.RemoveAt(0)
Catch ex As Exception
If ex.Message.ToLower.Contains("access to the path") Then
Continue While
Else
ret.ErrorMessage = ex.Message
ret.ListFiles.Clear()
Exit While
End If
End Try
End While
Return ret
End Function
Private Shared Function IsSystemFile(file As String) As Boolean
Try
If file.Contains("$"c) OrElse file.Contains("~"c) Then Return True
If IO.File.GetAttributes(file) = (IO.FileAttributes.Hidden) Then Return True
If IO.File.GetAttributes(file) = (IO.FileAttributes.Offline) Then Return True
If IO.File.GetAttributes(file) = (IO.FileAttributes.System) Then Return True
If IO.File.GetAttributes(file) = (IO.FileAttributes.Temporary) Then Return True
Catch ex As Exception
Return True ' file probably inaccessible
End Try
Return False
End Function

 
Dont forget to use Try...Catch...Blocks. You may need a backgroundworker - especially if user has any control over the selected files.
 
In these examples, the variables should be assigned as follows....
oldFile = string containing name of existing directory to be copied
newFile = string conatining the directory name of the directory that will be created
overwrite = boolean. If true and file already exists,it will be overwritten. If false an exiting file would cause an error
text string = New text to be added to end of file
ignore boolean - True=Ignore specific MetaData errors False=stop on any error
backup1 string = file name to for the backup

 
Append Data = IO.File.AppendAllText(oldFile, text) Delete File = IO.File.Delete(oldFile) Copy File = IO.File.Copy(oldFile, newFile, overwrite) If file already exists = If IO.File.Exists(oldFile) Then Move File = IO.File.Move(oldFile, newFile, overwrite) Move&Backup File = IO.File.Replace(oldFile, newFile, backup1, ignore)
 
This function will search an entire directory (or directory with sub directories) and list every file which contains a text string. However, it is likely to be unsuitable for your application due to one or more of the following considerations...

• Function should run in a background worker
• Function will fail with an "access denied" error when it encounters a locked file
  
• Searching files can be a slow process and the function does not provide progress reports
• There is no easy way to cancel command once it has started
• Function attempts to search every file, including images and binary files
• An inappropriate search (e.g. Search "C:\" for anything could hang current thread

Having explained why it is usually best to avoid FileSystem.FindInFiles based functions, there may be an exception - when you can tightly control the entire contents of the searched directory/sub-directories, the function should be able to perform the task far faster than a manually coded alternative.
 
Private Shared Function Find_in_Folder(folder As String, searchFor As String, ignoreCase As Boolean, includeSubSirectories As Boolean) As List(Of String)
Dim searchOpt As FileIO.SearchOption
Dim ret As New List(Of String)
If includeSubSirectories Then
searchOpt = FileIO.SearchOption.SearchAllSubDirectories
Else
searchOpt = FileIO.SearchOption.SearchTopLevelOnly
End If
Try
ret = My.Computer.FileSystem.FindInFiles(folder, searchFor, ignoreCase, searchOpt).ToList
Catch ex as Exception
Dim errorMessage as String = ex.Message
ret = {errorMessage}.toList
End Try
Return Ret
End Function

 

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