Object reference not set to an instance of an object?

Question

I have the following code to find a specific file in a directory & all its sub directories

Public Function DoRecursiveSearch(ByVal DirPath As String, _  
Optional ByVal FileSearchPattern As String = "*.*", _  
Optional ByVal FolderSearchPattern As String = "*", _  
Optional ByVal Recursive As Boolean = True) As ArrayList  
  
        ' Specify the directories you want to manipulate.  
        Dim di As System.IO.DirectoryInfo = New System.IO.DirectoryInfo(DirPath)  
        Dim ar As New ArrayList  
        Try  
            ' Get only subdirectories   
            Dim dirs As System.IO.FileSystemInfo() = di.GetDirectories(FolderSearchPattern)  
            Dim files As System.IO.FileSystemInfo()  
            Dim diNext As System.IO.DirectoryInfo  
            Dim fiNext As System.IO.FileInfo  
  
            files = di.GetFiles(FileSearchPattern)  
            For Each fiNext In files  
                ar.Add(fiNext)  
            Next  
  
            If Recursive Then  
                For Each diNext In dirs  
                    ar.AddRange(DoRecursiveSearch(diNext.FullName, FileSearchPattern, FolderSearchPattern, Recursive))  
                Next  
            End If  
  
            Return ar  
        Catch e As Exception  
            Console.WriteLine("The process failed: {0}", e.ToString())  
        End Try  
  
    End Function  
  
Public Function GetDirectoryLocation(ByVal SearchDir As String, ByVal searchFile As String) As String  
        '"C:\Program Files\Norton Security\"  
  
  
        Dim msg As String  
        Dim ar As New ArrayList  
        Dim fi As System.IO.FileInfo  
        'ar = GetFiles(Server.MapPath("."), "*.aspx")  
        ar = DoRecursiveSearch(SearchDir, searchFile)  
        'Response.Write("<Pre>")  
  
        For Each fi In ar  
            NortonLocation = fi.FullName  
            'msg = msg & "File Path: " & fi.FullName & vbCrLf  
            'msg = msg & "File Size: " & fi.Length & vbCrLf  
            'msg = msg & "Last Modified: " & fi.LastWriteTime & vbCrLf  
            'msg = msg & "---------------------------" & vbCrLf  
            'Console.WriteLine(msg)  
        Next  
        'Response.Write("</Pre>")  
        If NortonLocation = "" Then  
            MsgBox(SearchDir & "   " & searchFile & " not found")  
        Else  
            Return NortonLocation  
        End If  
    End Function  

in the function: "Function GetDirectoryLocation" the error is in the following line for "ar"

" For Each fi In ar"
the eror being: "Object reference not set to an instance of an object" located against "ar"

it works fine on windows 10 but creates this error when running under windows 11

any assistance to fix this would be most appreciated

Answer 1

When you encounter a directory that you do not have access to, your try/catch caught the error but you did not return ar.

Note the @MotoX80 comments.

The code is only finding the last occurrence of whatever file that you are looking for. Is that what you want?

Module Module1  
    Sub Main()  
        Dim x As String = ""  
        Dim arFiles As String  
        arFiles = GetDirectoryLocation("c:\", "EvanInHallway.jpg")  
        MsgBox(arFiles)  
    End Sub  
    Public Function DoRecursiveSearch(ByVal DirPath As String,  
Optional ByVal FileSearchPattern As String = "*.*",  
Optional ByVal FolderSearchPattern As String = "*",  
Optional ByVal Recursive As Boolean = True) As ArrayList  
  
        ' Specify the directories you want to manipulate.  
        Dim di As System.IO.DirectoryInfo = New System.IO.DirectoryInfo(DirPath)  
        Dim ar As New ArrayList  
        Try  
            ' Get only subdirectories   
            Dim dirs As System.IO.FileSystemInfo() = di.GetDirectories(FolderSearchPattern)  
            Dim files As System.IO.FileSystemInfo()  
            Dim diNext As System.IO.DirectoryInfo  
            Dim fiNext As System.IO.FileInfo  
  
            files = di.GetFiles(FileSearchPattern)  
            For Each fiNext In files  
                Console.WriteLine(fiNext.Name)  
                ar.Add(fiNext)  
            Next  
  
            If Recursive Then  
                For Each diNext In dirs  
                    ar.AddRange(DoRecursiveSearch(diNext.FullName, FileSearchPattern, FolderSearchPattern, Recursive))  
                Next  
            End If  
  
        Catch e As Exception  
            Console.WriteLine("The process failed: {0}", e.ToString())  
        End Try  
        Return ar                     ' @ MotoX80 you need to return the arraylist   
    End Function  
  
    Public Function GetDirectoryLocation(ByVal SearchDir As String, ByVal searchFile As String) As String  
        '"C:\Program Files\Norton Security\"  
        Dim NortonLocation As String = ""        ' @ MotoX80  undefined variable   
  
        Dim msg As String  
        Dim ar As New ArrayList  
        Dim fi As System.IO.FileInfo  
        'ar = GetFiles(Server.MapPath("."), "*.aspx")  
        ar = DoRecursiveSearch(SearchDir, searchFile)  
        'Response.Write("<Pre>")  
  
        For Each fi In ar  
            NortonLocation = fi.FullName  
            'msg = msg & "File Path: " & fi.FullName & vbCrLf  
            'msg = msg & "File Size: " & fi.Length & vbCrLf  
            'msg = msg & "Last Modified: " & fi.LastWriteTime & vbCrLf  
            'msg = msg & "---------------------------" & vbCrLf  
            'Console.WriteLine(msg)  
        Next  
        'Response.Write("</Pre>")  
        If NortonLocation = "" Then  
            MsgBox(SearchDir & "   " & searchFile & " not found")  
        End If  
        Return NortonLocation        ' @ MotoX80 we only return the first occurrance????   
    End Function  
End Module  
  

Answer 2

Thanks for taking an interest in my project
The changes you made were applied & it works fine.

Thank you, much appreciated