Web source: off-screen WebView2 capture + layout persistence + transparent bg
Bundle exception (2026-08-27): this lands prior-session work plus today's transparency fix as one commit per creator instruction. WebView2Manager (new): off-screen WebView2 control parked at -5000/-5000 in the window's visual tree, captures via CapturePreviewAsync every 100 ms into a BGRA8 VideoFrame. Source Width/Height sync to the control via PropertyChanged. JS transparent-background injection runs on every NavigationStarting/NavigationCompleted so the page's own CSS does not paint white over the capture. Transparency fix: DefaultBackgroundColor = System.Drawing.Color.Transparent set on the WPF control before EnsureCoreWebView2Async. The WPF SDK doc says the value is forwarded to the controller on init; the IDL (ICoreWebView2- Controller2) confirms alpha=0 makes the capture alpha-preserving. The prior-session 'CoreWebView2.BackgroundColor' path was the wrong property name and has been replaced. LayoutStore: WebUri column added (idempotent ALTER TABLE) and round-tripped on save/load (schema v11). MainViewModel: WebView2Manager constructed on Loaded; loaded web sources re-registered; Source.WebUri PropertyChanged forwards to manager. MainWindow: off-screen host Canvas added to visual tree. Tests: 3 scale-sync + WebView2_DefaultBackgroundColor_Is_Transparent + LayoutStorePersistenceTests.WebSource_WebUri_Persists. 234/236 pass (2 pre-existing failures unchanged). Scale bug (DPI/physical-pixel mismatch) still open.
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using System;
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using System.Drawing;
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using System.IO;
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using System.Windows;
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using System.Windows.Controls;
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using System.Windows.Media;
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using System.Windows.Media.Imaging;
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using System.Windows.Threading;
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using Microsoft.Web.WebView2.Core;
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using Microsoft.Web.WebView2.Wpf;
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using ytLive.Helpers;
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using ytLive.Models;
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namespace ytLive.Services;
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public sealed class WebView2Manager : IDisposable
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{
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private readonly Panel _hostPanel;
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private readonly Dispatcher _dispatcher;
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private readonly Dictionary<string, WebSourceSession> _sessions = new();
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public event Action<string, WriteableBitmap>? PreviewBitmapChanged;
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private sealed class WebSourceSession
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{
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public required WebView2 Control { get; init; }
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public required DispatcherTimer CaptureTimer { get; init; }
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public VideoFrame? LatestFrame;
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public bool Disposed;
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public bool Initialized;
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}
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public WebView2Manager(Panel hostPanel, Dispatcher dispatcher)
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{
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_hostPanel = hostPanel;
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_dispatcher = dispatcher;
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}
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public void Register(Source source)
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{
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if (_sessions.ContainsKey(source.Id)) return;
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var webView = new WebView2
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{
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Width = source.Width > 0 ? source.Width : 640,
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Height = source.Height > 0 ? source.Height : 480,
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DefaultBackgroundColor = System.Drawing.Color.Transparent,
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Visibility = System.Windows.Visibility.Visible,
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};
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Canvas.SetLeft(webView, -5000);
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Canvas.SetTop(webView, -5000);
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_hostPanel.Children.Add(webView);
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var timer = new DispatcherTimer
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{
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Interval = TimeSpan.FromMilliseconds(100),
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};
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var session = new WebSourceSession
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{
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Control = webView,
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CaptureTimer = timer,
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};
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_sessions[source.Id] = session;
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source.PropertyChanged += (_, e) =>
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{
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if (e.PropertyName == nameof(Source.Width) || e.PropertyName == nameof(Source.Height))
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{
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var w = Math.Max(1, (int)source.Width);
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var h = Math.Max(1, (int)source.Height);
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if (Math.Abs(session.Control.Width - w) > 0.5 ||
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Math.Abs(session.Control.Height - h) > 0.5)
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{
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session.Control.Width = w;
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session.Control.Height = h;
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}
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}
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};
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timer.Tick += (_, _) =>
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{
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if (!session.Disposed && session.Initialized)
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_ = CaptureFrame(source.Id);
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};
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_ = InitializeAsync(source, session);
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}
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public void Unregister(string sourceId) => RemoveSession(sourceId);
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public void OnWebUriChanged(Source source)
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{
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if (!_sessions.TryGetValue(source.Id, out var session)) return;
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if (session.Disposed || !session.Initialized) return;
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if (string.IsNullOrEmpty(source.WebUri))
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{
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session.LatestFrame = null;
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session.Control.CoreWebView2?.NavigateToString(
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"<html><body style='background:transparent;margin:0'></body></html>");
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return;
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}
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Navigate(source.WebUri, session);
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}
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public VideoFrame? GetLatestFrame(string sourceId)
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{
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return _sessions.TryGetValue(sourceId, out var session) ? session.LatestFrame : null;
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}
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private async Task InitializeAsync(Source source, WebSourceSession session)
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{
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try
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{
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await session.Control.EnsureCoreWebView2Async();
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var cws = session.Control.CoreWebView2!;
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cws.NavigationStarting += (_, e) =>
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{
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_ = cws.ExecuteScriptAsync(
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"document.documentElement.style.background='transparent';" +
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"document.body.style.background='transparent';");
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};
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cws.NavigationCompleted += (_, _) =>
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{
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_ = cws.ExecuteScriptAsync(
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"document.documentElement.style.background='transparent';" +
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"document.body.style.background='transparent';");
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};
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session.Initialized = true;
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session.Control.CoreWebView2.NavigateToString(
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"<html><body style='background:transparent;margin:0'></body></html>");
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if (!string.IsNullOrEmpty(source.WebUri))
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Navigate(source.WebUri, session);
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session.CaptureTimer.Start();
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}
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catch (Exception ex)
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{
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AppLog.Write($"WebView2Manager: init failed for '{source.Name}': {ex.Message}");
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RemoveSession(source.Id);
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}
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}
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private void Navigate(string url, WebSourceSession session)
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{
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try { session.Control.CoreWebView2?.Navigate(url); }
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catch (Exception ex) { AppLog.Write($"WebView2Manager: navigate failed: {ex.Message}"); }
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}
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private async Task CaptureFrame(string sourceId)
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{
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if (!_sessions.TryGetValue(sourceId, out var session) || session.Disposed) return;
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try
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{
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var webView = session.Control;
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if (webView.CoreWebView2 == null) return;
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using var ms = new MemoryStream();
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await webView.CoreWebView2.CapturePreviewAsync(
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CoreWebView2CapturePreviewImageFormat.Png, ms);
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ms.Position = 0;
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var bitmap = new BitmapImage();
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bitmap.BeginInit();
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bitmap.StreamSource = ms;
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bitmap.CacheOption = BitmapCacheOption.OnLoad;
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bitmap.EndInit();
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bitmap.Freeze();
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var formatted = new FormatConvertedBitmap(bitmap,
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PixelFormats.Bgra32, null, 0);
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var pixW = formatted.PixelWidth;
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var pixH = formatted.PixelHeight;
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if (pixW < 1 || pixH < 1) return;
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var pixels = new byte[pixW * pixH * 4];
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formatted.CopyPixels(pixels, pixW * 4, 0);
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var stride = pixW * 4;
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var wb = new WriteableBitmap(pixW, pixH, 96, 96, PixelFormats.Bgra32, null);
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wb.WritePixels(new Int32Rect(0, 0, pixW, pixH), pixels, stride, 0);
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wb.Freeze();
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session.LatestFrame = new VideoFrame(pixW, pixH, pixels);
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_ = _dispatcher.BeginInvoke(() =>
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{
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PreviewBitmapChanged?.Invoke(sourceId, wb);
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});
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}
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catch (ObjectDisposedException) { }
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catch (InvalidOperationException) { }
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catch (Exception ex)
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{
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AppLog.Write($"WebView2Manager: capture failed for '{sourceId}': {ex.Message}");
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}
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}
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private void RemoveSession(string sourceId)
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{
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if (!_sessions.TryGetValue(sourceId, out var session)) return;
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session.Disposed = true;
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session.CaptureTimer.Stop();
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_hostPanel.Children.Remove(session.Control);
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try { session.Control.Dispose(); } catch { }
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_sessions.Remove(sourceId);
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}
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public void Dispose()
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{
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foreach (var id in _sessions.Keys.ToList())
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RemoveSession(id);
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}
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}
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