First in Visual Basic .NET
When you program, if the task in your loop is the same over and over, you might want to recycle some code from your program. This will multiply the power of your power by 2, by 5 or 10 and make your code shorter.
Here is an example from a previous post. The sample code in Visual Basic will search for all the files with a pattern in a directory/subdirectory and list them in a ListBox. Isn�t that great? Yes and no. Even with the best tactic to speed up your code, you will wait forever if the directory has a lot of subdirectories with a lot of files.
Old code: search file without recursive feature
Private Sub findfiles() Dim dirPath As String Dim path_valid As Boolean path_valid = True dirPath = "c:\temp\" ' temp = no access problem dirPath = "c:\System Recovery" ' System Recovery = access problem '---------------------------------------------- ' CHECK PATH IF VALID '---------------------------------------------- 'trim the sPath to remove space before and after the String dirPath = Trim(dirPath) 'check if sPath is not zero length If Len(dirPath) > 0 Then Else path_valid = False End If 'check for invalid char ' \ * | : ? < > / except the \ because is a directory seperator ' and * that means to ignore whatever inside the other chars. (optional) If InStr(dirPath, "|", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, ">", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, "<", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, "?", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, ":", CompareMethod.Binary) = 2 Then 'very basic way to check if there is a ":" in the Path. Dim str_temp As String = dirPath.Substring(2, Len(dirPath) - 2) If InStr(str_temp, ":", CompareMethod.Binary) > 0 Then path_valid = False End If End If If InStr(dirPath, "*", CompareMethod.Binary) > 0 Then path_valid = False End If 'be careful with non-english caracters '---------------------------------------------- ' SECURITY '---------------------------------------------- Dim oDirectorySecurity As System.Security.AccessControl.DirectorySecurity Dim oAuthorizationRuleCollection As System.Security.AccessControl.AuthorizationRuleCollection Dim oRule As System.Security.AccessControl.FileSystemAccessRule Dim Security_valid As Boolean Security_valid = False oDirectorySecurity = IO.Directory.GetAccessControl(dirPath) oAuthorizationRuleCollection = oDirectorySecurity.GetAccessRules(True, True, Type.GetType("System.Security.Principal.NTAccount")) For Each oRule In oAuthorizationRuleCollection If oRule.FileSystemRights = Security.AccessControl.FileSystemRights.FullControl Then If InStr(oRule.IdentityReference.Value, My.User.Name) > 0 Then Security_valid = True End If End If Next '---------------------------------------------- ' SECURITY '---------------------------------------------- Dim Is_Folder_shortcut As Boolean Is_Folder_shortcut = False If dirPath.StartsWith("c:\Users", True, System.Globalization.CultureInfo.CurrentCulture) Then 'very basic way to force you to be very carefull with that folder Is_Folder_shortcut = True End If '---------------------------------------------- ' IF ALL OK, THEN DISPLAY THE RESULT '---------------------------------------------- If oForm2 Is Nothing OrElse oForm2.IsDisposed Then oForm2 = New Form2 oForm2.Show() End If oForm2.ListBox1.Items.Clear() If path_valid = True And Security_valid = True And Is_Folder_shortcut = False Then For Each foundFile As String In My.Computer.FileSystem.GetFiles( _ dirPath, FileIO.SearchOption.SearchAllSubDirectories, "*.dll") oForm2.ListBox1.Items.Add(foundFile) Next Else MsgBox("path_valid =" & path_valid & vbCrLf & "Security_valid =" & Security_valid) End If End Sub |
Now, this is a new code with minor change. All modifications are highlighted in yellow.
Private Sub findfiles(Optional dirPath As String = "c:\temp\", Optional String_to_Search As String = "*.dll") 'Dim dirPath As String ' you need to put in argument a "top" directory (optional if you want) Dim path_valid As Boolean path_valid = True 'dirPath = "c:\temp\" ' temp = no access problem 'dirPath = "c:\System Recovery" ' System Recovery = access problem '---------------------------------------------- ' CHECK PATH IF VALID '---------------------------------------------- 'trim the sPath to remove space before and after the String dirPath = Trim(dirPath) 'check if sPath is not zero length If Len(dirPath) > 0 Then Else path_valid = False End If 'check for invalid char ' \ * | : ? < > / except the \ because is a directory seperator ' and * that means to ignore whatever inside the other chars. (optional) If InStr(dirPath, "|", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, ">", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, "<", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, "?", CompareMethod.Binary) > 0 Then path_valid = False End If If InStr(dirPath, ":", CompareMethod.Binary) = 2 Then 'very basic way to check if there is a ":" in the Path. Dim str_temp As String = dirPath.Substring(2, Len(dirPath) - 2) If InStr(str_temp, ":", CompareMethod.Binary) > 0 Then path_valid = False End If End If If InStr(dirPath, "*", CompareMethod.Binary) > 0 Then path_valid = False End If 'be careful with non-english caracters '---------------------------------------------- ' SECURITY '---------------------------------------------- Dim oDirectorySecurity As System.Security.AccessControl.DirectorySecurity Dim oAuthorizationRuleCollection As System.Security.AccessControl.AuthorizationRuleCollection Dim oRule As System.Security.AccessControl.FileSystemAccessRule Dim Security_valid As Boolean Security_valid = False oDirectorySecurity = IO.Directory.GetAccessControl(dirPath) oAuthorizationRuleCollection = oDirectorySecurity.GetAccessRules(True, True, Type.GetType("System.Security.Principal.NTAccount")) For Each oRule In oAuthorizationRuleCollection If oRule.FileSystemRights = Security.AccessControl.FileSystemRights.FullControl Then If InStr(oRule.IdentityReference.Value, My.User.Name) > 0 Then Security_valid = True End If End If Next '---------------------------------------------- ' SECURITY '---------------------------------------------- Dim Is_Folder_shortcut As Boolean Is_Folder_shortcut = False If dirPath.StartsWith("c:\Users", True, System.Globalization.CultureInfo.CurrentCulture) Then 'very basic way to force you to be very carefull with that folder Is_Folder_shortcut = True End If '---------------------------------------------- ' IF ALL OK, THEN DISPLAY THE RESULT '---------------------------------------------- If oForm2 Is Nothing OrElse oForm2.IsDisposed Then oForm2 = New Form2 oForm2.Show() End If 'oForm2.ListBox1.Items.Clear() ' recursive search file : don't clear the listBox If path_valid = True And Security_valid = True And Is_Folder_shortcut = False Then For Each foundFile As String In My.Computer.FileSystem.GetFiles( _ dirPath, FileIO.SearchOption.SearchTopLevelOnly, String_to_Search) 'recursive search file : you need to limit your search to 1 single directory : and put extention in search argument oForm2.ListBox1.Items.Add(foundFile) Next For Each foundDirectory As String In My.Computer.FileSystem.GetDirectories(dirPath, FileIO.SearchOption.SearchTopLevelOnly) findfiles(foundDirectory) ''recursive search file : re-use "himself" Next Else MsgBox("path_valid =" & path_valid & vbCrLf & "Security_valid =" & Security_valid) End If End Sub |
Here is the explanation and I will try to keep it short. Instead of asking the My.Computer.FileSystem.GetFiles to seach for all files in all subDirectories in 1 single operation, we ask the findfiles function to limit his search on the top level directory.
For all other directory or subdirectory, we re-call the same findfiles function to do the same operation. The program will loop himself until there are no more directory to look for.
Is like asking the computer to play chess with himself.
Because you are able to separate 1 single big search to multiples tiny search, you will be able to multi-thread the while operation.
Good to read:
Previous Post : Search a file
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