Feature: Improved performance when compressing files

[aftab23822]

Report: File Size Calculation Freezing Issue

1. Problem Overview

Our WPF application was becoming unresponsive ("Not Responding" state) when performing file size calculations on large directories.

• Example: scanning folders with 50,000+ files caused the UI to freeze for several seconds or indefinitely.
• This created a poor user experience, as the app appeared frozen and Windows would show it as not responding.

Closes #14306

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2. Investigation

We used Visual Studio Performance Profiler (CPU Usage tool) to understand where the app was spending time.

Findings:

• Almost all CPU time was spent in file size calculation routines.
• The entire computation was happening in a single, long-running synchronous task, blocking the UI thread.
• Because WPF apps rely on the UI thread to redraw and respond to input, the UI became unresponsive during this work.

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3. Root Cause

• File size computation was being performed in a tight loop across thousands of files.
• No opportunity for the UI thread to "breathe" (yield execution).
• As a result, even though the calculation eventually completed, the user perceived the app as frozen.

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4. Solution

We redesigned the FileSizeCalculator to:

1. Introduce async/await – run expensive work without blocking the UI thread.
2. Batch processing (chunking) – process files in groups (e.g., 1000 at a time). After each batch, yield control back to the system so the UI remains responsive.
3. Efficient file access via Win32 API (CreateFile, GetFileSizeEx) – avoids unnecessary overhead of FileInfo for each file.
4. ConcurrentDictionary caching – prevents recalculating file sizes repeatedly.
5. Cancellation support – users can cancel ongoing operations.

Example snippet (batch logic):

if (batch.Count >= ChunkSize)
{
    ComputeFileSizeBatch(batch);
    batch.Clear();
    await Task.Yield(); // let UI update
}

FileSizeCalculator Report.docx

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5. Results

• Tested with 50,000+ files.
• The calculation now completes successfully without UI freezing.
• Application remains responsive (user can move/resize window, cancel operation, see progress).
• Performance improved due to batching and efficient native calls.

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6. Key Takeaways

• Long-running operations in WPF must not block the UI thread.
• Chunking and async/await is a reliable pattern for large data processing.
• Profiling tools (like Visual Studio CPU Usage) are essential for identifying hotspots.

[Josh65-2201]

Based on C:\Windows\WinSxS after the folder loaded and was just the folder calculations, for 4.0.11 it was about 8% CPU usage and 58 seconds, this PR was about 8% CPU usage but 1 minute slower to show total folder size on the status bar.

C: and C:\Windows\System32 where similar CPU and time on 4.0.11 and this PR

[Copilot]

Pull Request Overview

This PR improves the performance and responsiveness of file size calculations in the WPF application by replacing a blocking synchronous approach with an asynchronous batch processing system. The changes address UI freezing issues when processing large directories (50,000+ files).

• Replaced Win32 FindFirstFileEx/FindNextFile API calls with managed Directory.Enumerate methods
• Implemented batched processing with Task.Yield() to maintain UI responsiveness
• Introduced a new ComputeFileSizeBatch method for efficient batch file size computation

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[aftab23822]

Looking forward to implementing CoPilot Ai's suggestions in the PR. Also looking to improve performance as per @Josh65-2201's suggestion.

[aftab23822]

Based on C:\Windows\WinSxS after the folder loaded and was just the folder calculations, for 4.0.11 it was about 8% CPU usage and 58 seconds, this PR was about 8% CPU usage but 1 minute slower to show total folder size on the status bar.

C: and C:\Windows\System32 where similar CPU and time on 4.0.11 and this PR

Hi @Josh65-2201,
I’ve verified that the method FileSizeCalculator.ComputeSizeAsync is not used when checking file/folder details.
It’s only invoked during operations like copy, move, delete, or archive.

Thanks.