The Goal

We want to:

1. Search through subfolders automatically.
2. Add a maxDepth parameter so we don’t accidentally crawl the entire hard drive.
3. Keep the simple version working using method overloading.

Step 1: Move File Reading to its own Method

The original FindInFiles function did everything: validated the folder, looped through children, read file content, and matched text. Adding recursion to that would make the code look ugly, so let’s refactor our code.

We’ll start by moving the file-reading logic into its own private method: SearchFile. This keeps the “search” logic separate from the “looping” logic.

Private Sub SearchFile(file As FolderItem, searchTerm As String, hits() As SearchHit)
  Try
    Var input As TextInputStream = TextInputStream.Open(file)
    input.Encoding = Encodings.UTF8
    Var lineNumber As Integer = 0
    While Not input.EndOfFile
      Var line As String = input.ReadLine
      lineNumber = lineNumber + 1
      If line.Contains(searchTerm, ComparisonOptions.CaseInsensitive) Then
        hits.Add(New SearchHit(file.NativePath, lineNumber, line))
      End If
    Wend
    input.Close
  Catch error As IOException
    // Skip unreadable files
  End Try
End Sub

Step 2: Recursive Folder Traversal

Now we create SearchFolder. This method loops through a folder. If it finds a file, it calls SearchFile. If it finds a folder, it calls itself.

To keep this safe, we Use maxDepth:

• maxDepth = 0: Search only this folder.
• maxDepth > 0: Search this folder and N levels of subfolders.
• maxDepth = -1: Search everything (unlimited).

Private Sub SearchFolder(folder As FolderItem, searchTerm As String, hits() As SearchHit, maxDepth As Integer)
   Try
    For Each item As FolderItem In folder.Children
      If item Is Nil Or Not item.Exists Or Not item.IsReadable Then Continue
      If item.IsFolder Then
        If maxDepth <> 0 Then
          Var nextDepth As Integer = If(maxDepth > 0, maxDepth - 1, maxDepth)
          SearchFolder(item, searchTerm, hits, nextDepth)
        End If
      Else
        SearchFile(item, searchTerm, hits)
      End If
    Next
  Catch error As IOException
    // Skip inaccessible folders
  End Try
End Sub

The logic in nextDepth lets us count down if there’s a limit, or stay at -1 if there isn’t.

Step 3: Support Both Versions with Method Overloading

Overloading is a feature that lets you have multiple methods with the same name, as long as they have different parameters. In our case, it allows us to provide a simple version for one folder, and a recursive version with a depth limit. Xojo will automatically pick the right one based on the arguments you pass. You can read more about it in the Xojo Documentation.

The default version (depth 0):

Public Function FindInFiles(targetFolder As FolderItem, searchTerm As String) As SearchHit()
  Return FindInFiles(targetFolder, searchTerm, 0)
End Function

The recursive version:

Public Function FindInFiles(targetFolder As FolderItem, searchTerm As String, maxDepth As Integer) As SearchHit()
  Var hits() As SearchHit
  If targetFolder Is Nil Or Not targetFolder.Exists Or Not targetFolder.IsFolder Or searchTerm.IsEmpty Then
    Return hits
  End If
  Try
    SearchFolder(targetFolder, searchTerm, hits, maxDepth)
  Catch error As IOException
    // Skip inaccessible folders
  End Try
  Return hits
End Function

By separating the validation, traversal, and processing, the code is much easier to modify. If you want to add Regex support, you only change SearchFile. If you want to filter by file extension, you only change SearchFolder.

Summary

Now, you can search a single folder just like before, or crawl a directory tree with one extra parameter:

// Search up to 3 levels deep
Var results() As SearchUtils.SearchHit = SearchUtils.FindInFiles(myFolder, "TODO", 3)

The Complete Recursive Code

The SearchUtils Module

Module SearchUtils

  Class SearchHit
    Public Property FilePath As String
    Public Property LineNumber As Integer
    Public Property LineText As String

    Public Sub Constructor(filePath As String, lineNumber As Integer, lineText As String)
      Self.FilePath = filePath
      Self.LineNumber = lineNumber
      Self.LineText = lineText
    End Sub
  End Class

  Public Function FindInFiles(targetFolder As FolderItem, searchTerm As String) As SearchHit()
    // Simple usage: depth = 0
    Return FindInFiles(targetFolder, searchTerm, 0)
  End Function

  Public Function FindInFiles(targetFolder As FolderItem, searchTerm As String, maxDepth As Integer) As SearchHit()
    // Recursive usage: maxDepth ( -1 is unlimited )

    Var hits() As SearchHit

    If targetFolder Is Nil Or Not targetFolder.Exists Or Not targetFolder.IsFolder Or searchTerm.IsEmpty Then
      Return hits
    End If

    Try
      SearchFolder(targetFolder, searchTerm, hits, maxDepth)
    Catch error As IOException
      // Skip inaccessible folders
    End Try

    Return hits
  End Function

  Private Sub SearchFolder(folder As FolderItem, searchTerm As String, hits() As SearchHit, maxDepth As Integer)
    Try
      For Each item As FolderItem In folder.Children
        If item Is Nil Or Not item.Exists Or Not item.IsReadable Then Continue

        If item.IsFolder Then
          If maxDepth <> 0 Then
            Var nextDepth As Integer = If(maxDepth > 0, maxDepth - 1, maxDepth)
            SearchFolder(item, searchTerm, hits, nextDepth)
          End If
        Else
          SearchFile(item, searchTerm, hits)
        End If
      Next
    Catch error As IOException
      // Skip inaccessible folders
    End Try
  End Sub

  Private Sub SearchFile(file As FolderItem, searchTerm As String, hits() As SearchHit)
    Try
      Var input As TextInputStream = TextInputStream.Open(file)
      input.Encoding = Encodings.UTF8
      Var lineNumber As Integer = 0

      While Not input.EndOfFile
        Var line As String = input.ReadLine
        lineNumber = lineNumber + 1

        If line.Contains(searchTerm, ComparisonOptions.CaseInsensitive) Then
          hits.Add(New SearchHit(file.NativePath, lineNumber, line))
        End If
      Wend

      input.Close
    Catch error As IOException
      // Skip unreadable files
    End Try
  End Sub
End Module

Happy coding!

Gabriel is a digital marketing enthusiast who loves coding with Xojo to create cool software tools for any platform. He is always eager to learn and share new ideas!

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In this post, we’ll build a simple Find in Files utility in Xojo that:

• searches the files in a folder
• reads each file line by line
• performs a plain-text, case-insensitive match
• returns the file path, line number, and matching line

The goal is simple: build something useful while leaving the door open for the fancier stuff.

What this Find in Files function will do

Let’s keep the scope clear:

• search one folder
• search plain text only
• skip subfolders for now
• return the matching file path, line number, and line contents

Step 1: A class in a module and some properties

Before touching the file system, let’s define what a match looks like.

You could return raw strings, but that gets messy fast. A small class keeps the code readable and gives us an obvious place to extend later. In this version, I like keeping that class inside the same module as the search function. It keeps the entire utility self-contained instead of spraying helper types all over the project.

So, we start by adding a module SearchUtils and inside the module we will add a class SearchHit.

Module SearchUtils

  Class SearchHit

    Public Property FilePath As String
    Public Property LineNumber As Integer
    Public Property LineText As String

    Public Sub Constructor(filePath As String, lineNumber As Integer, lineText As String)
      Self.FilePath = filePath
      Self.LineNumber = lineNumber
      Self.LineText = lineText
    End Sub

  End Class

End Module

Each result stores three things:

1. the file path
2. the line number
3. the matching line

Step 2: Walk through the folder

FolderItem.Children lets us loop through a folder with a For Each loop, which keeps the code clear.

We’ll also reject bad input early:

• the folder is Nil
• the folder does not exist
• the item passed is not actually a folder
• the search term is empty

This process is simple, fast and effective.

Step 3: Read files line by line

For text files, TextInputStream.Open is the right tool. From there, we can call ReadLine until EndOfFile becomes True.

I prefer this over ReadAll for a utility like this. ReadAll is fine when the file is small and you know what you’re doing, but line-by-line reading is a better default here. It keeps memory use in check and gives us line numbers for free.

For the sample code, I’m explicitly using UTF-8:

input.Encoding = Encodings.UTF8

That keeps the sample predictable. It does not mean this code can gracefully decode every text file you throw at it. Files with unknown encodings or binary-ish content are a separate problem, and they deserve their own solution.

Step 4: Match the text

For a plain-text search, String.Contains does exactly what we need:

line.Contains(searchTerm, ComparisonOptions.CaseInsensitive)

It handles the case-insensitivity without the overhead, or the headache, of regex.

Step 5: The full module and class and function

Module SearchUtils

  Public Class SearchHit
    Public Property FilePath As String
    Public Property LineNumber As Integer
    Public Property LineText As String

    Public Sub Constructor(filePath As String, lineNumber As Integer, lineText As String)
      Self.FilePath = filePath
      Self.LineNumber = lineNumber
      Self.LineText = lineText
    End Sub
  End Class

  Public Function FindInFiles(targetFolder As FolderItem, searchTerm As String) As SearchHit()
    Var hits() As SearchHit

    If targetFolder Is Nil Then
      Return hits
    End If

    If Not targetFolder.Exists Or Not targetFolder.IsFolder Then
      Return hits
    End If

    If searchTerm.IsEmpty Then
      Return hits
    End If

    For Each item As FolderItem In targetFolder.Children
      If item Is Nil Then Continue
      If item.IsFolder Then Continue
      If Not item.Exists Then Continue
      If Not item.IsReadable Then Continue

      Try
        Var input As TextInputStream = TextInputStream.Open(item)
        input.Encoding = Encodings.UTF8

        Var lineNumber As Integer = 0

        While Not input.EndOfFile
          Var line As String = input.ReadLine
          lineNumber = lineNumber + 1

          If line.Contains(searchTerm, ComparisonOptions.CaseInsensitive) Then
            hits.Add(New SearchHit(item.NativePath, lineNumber, line))
          End If
        Wend

        input.Close

      Catch error As IOException
        ' Skip files that cannot be read as text.
        Continue
      End Try
    Next

    Return hits
  End Function

End Module

How it works

Let’s break down the important parts.

Input validation

This block prevents pointless work and avoids avoidable runtime problems:

If targetFolder Is Nil Then
  Return hits
End If

If Not targetFolder.Exists Or Not targetFolder.IsFolder Then
  Return hits
End If

If searchTerm.IsEmpty Then
  Return hits
End If

Rule of thumb: reject bad input early.

Folder iteration

This is the core loop:

For Each item As FolderItem In targetFolder.Children

We’re only scanning the folder’s immediate contents. If an item is another folder, we skip it.

If item.IsFolder Then Continue

Safe text reading

Each file is opened with TextInputStream.Open inside a Try...Catch block:

Try
  Var input As TextInputStream = TextInputStream.Open(item)
  input.Encoding = Encodings.UTF8
  ...
Catch error As IOException
  Continue
End Try

That way, one unreadable file does not take down the whole search. It gets skipped and the rest of the folder still gets processed.

Line-by-line matching

This is where the actual work happens:

While Not input.EndOfFile
  Var line As String = input.ReadLine
  lineNumber = lineNumber + 1

  If line.Contains(searchTerm, ComparisonOptions.CaseInsensitive) Then
    hits.Add(New SearchHit(item.NativePath, lineNumber, line))
  End If
Wend

Because we’re reading one line at a time, attaching the correct line number is trivial.

Why keep SearchHit inside the module?

Because it belongs to this utility. The search function and its result type are part of the same little unit of behavior, so keeping them together makes the project easier to scan and easier to transform it to a Library.

It also means code outside the module uses the namespaced type:

Var results() As SearchUtils.SearchHit = SearchUtils.FindInFiles(folder, "xojo")

Using the function

Here’s a simple example that lets the user choose a folder and then writes the results to the debug log:

Var folder As FolderItem = FolderItem.ShowSelectFolderDialog
If folder Is Nil Then Return

Var results() As SearchUtils.SearchHit = SearchUtils.FindInFiles(folder, "error")

For Each hit As SearchUtils.SearchHit In results
  System.DebugLog(hit.FilePath + " | line " + hit.LineNumber.ToString + " | " + hit.LineText)
Next

If you want to display the results in a DesktopListBox, that works nicely too:

Var folder As FolderItem = FolderItem.ShowSelectFolderDialog
If folder Is Nil Then Return

Var results() As SearchUtils.SearchHit = FindInFiles(folder, "error")

ListBox1.RemoveAllRows
ListBox1.ColumnCount = 3

For Each hit As SearchUtils.SearchHit In results
  ListBox1.AddRow(hit.FilePath)
  ListBox1.CellTextAt(ListBox1.LastAddedRowIndex, 1) = hit.LineNumber.ToString
  ListBox1.CellTextAt(ListBox1.LastAddedRowIndex, 2) = hit.LineText
Next

A few sample results might look like this:

C:\Logs\app.log | line 18 | Error connecting to database
C:\Logs\app.log | line 42 | Error writing audit record
C:\Configs\service.txt | line 7 | Last error message: timeout

Practical limitations of this version

This utility is useful, but limited.

It assumes UTF-8

That is fine for plenty of modern text files, but not all of them. If you’re dealing with mixed encodings, you’ll need a smarter approach that detects the file encoding.

It doesn’t recurse into subfolders

That is deliberate. Recursive search is useful, but it adds another layer of behavior and another place to make the code harder to read.

Final thoughts

A basic Find in Files function is one of those utilities that looks small but pays off quickly. This is a base-layer utility. Once you have this working, adding recursion or regex is a much smaller lift.

Let’s discuss in the forums.

Gabriel is a digital marketing enthusiast who loves coding with Xojo to create cool software tools for any platform. He is always eager to learn and share new ideas!

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