PowerPoint typically operates within a single process, causing sequential blocking when handling multiple large presentations (e.g., >1GB). This often leads to unresponsive instances, hindering all operations. Terminating and restarting unresponsive processes provides limited relief but fails when processing numerous large files concurrently.

A robust solution involves launching PowerPoint under distinct user accounts. Each user session runs in a separate process, enabling parallel operations. This approach requires programmatically creating users (with administrative privileges) or pre-configuring accounts via Windows settings.

Control processes for each PowerPoint instance communicate via inter-process channels (e.g., pipes, WM_COPYDATA). These channels relay commands (open, navigate, media control) to worker processes operating under designated credentials.

Process Initialization with Alternate Credentials

public void LaunchWithCredentials(string executablePath, string username, string password, string arguments)
{
    using (var securePassword = new SecureString())
    {
        foreach (char c in password ?? string.Empty)
            securePassword.AppendChar(c);

        var processInfo = new ProcessStartInfo
        {
            FileName = executablePath,
            Arguments = arguments,
            UserName = username,
            Password = securePassword,
            Domain = ".",
            LoadUserProfile = true,
            UseShellExecute = false
        };

        Process.Start(processInfo);
    }
}

PowerPoint Interaction Operations

private Application InitializePowerPoint() => new Application();

private void TerminatePowerPoint(ref Application pptInstance)
{
    try
    {
        pptInstance?.Quit();
    }
    catch (Exception ex) { /* Log error */ }
    finally
    {
        pptInstance = null;
        GC.Collect();
    }
}

public void OpenPresentation(Application pptApp, string filePath)
{
    if (pptApp == null) return;

    filePath = filePath.Replace('/', '\\');

    try
    {
        // Open read-only with placeholder password to prevent lock
        Presentation pres = pptApp.Presentations.Open(
            $"{filePath}::DummyPassword",
            ReadOnly: MsoTriState.msoTrue,
            Untitled: MsoTriState.msoTrue,
            WithWindow: MsoTriState.msoFalse);

        // Extract dimensions and slide count
        double width = pres.PageSetup.SlideWidth;
        double height = pres.PageSetup.SlideHeight;
        int slideCount = pres.Slides.Count;

        SlideShowWindow showWindow = pres.SlideShowSettings.Run();
    }
    catch (Exception ex) { /* Handle error */ }
}

public void CloseShow(SlideShowWindow window)
{
    try { window?.View.Exit(); }
    catch { /* Ignore */ }
}

public void NavigateToSlide(SlideShowWindow window, int slideIndex)
{
    try { window?.View.GotoSlide(slideIndex); }
    catch { /* Ignore */ }
}

public void AdvanceSlide(SlideShowWindow window)
{
    try { window?.View.Next(); }
    catch { /* Ignore */ }
}

public void RetreatSlide(SlideShowWindow window)
{
    try { window?.View.Previous(); }
    catch { /* Ignore */ }
}

Reference

• Enabling Concurrent PowerPoint Process Execution