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Fix null-forgiving operator misuse in System.Diagnostics.EventLog #126639

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Merged
tarekgh merged 2 commits into from
Sep 17, 2026
Merged

Fix null-forgiving operator misuse in System.Diagnostics.EventLog #126639

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831d871
Fix null-forgiving operator misuse in EventLogTraceListener and Event…
Copilot Apr 8, 2026
361889f
Address EventLog nullable review feedback
krwq Sep 17, 2026
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6 changes: 3 additions & 3 deletions src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLog.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1014,7 +1014,7 @@ public static void WriteEntry(string source, string? message, EventLogEntryType

public static void WriteEntry(string source, string? message, EventLogEntryType type, int eventID, short category, byte[]? rawData)
{
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null! /* Special case - EventLogInternal instance is immediately used */))
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null))
{
log.WriteEntry(message, type, eventID, category, rawData);
}
Expand All @@ -1037,15 +1037,15 @@ public void WriteEvent(EventInstance instance, byte[]? data, params object?[]? v

public static void WriteEvent(string source, EventInstance instance, params object?[]? values)
{
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null! /* Special case - EventLogInternal instance is immediately used */))
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null))
{
log.WriteEvent(instance, null, values);
}
}

public static void WriteEvent(string source, EventInstance instance, byte[] data, params object?[]? values)
{
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null! /* Special case - EventLogInternal instance is immediately used */))
using (EventLogInternal log = new EventLogInternal(string.Empty, ".", CheckAndNormalizeSourceName(source), parent: null))
{
log.WriteEvent(instance, data, values);
}
Expand Down
22 changes: 12 additions & 10 deletions src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogInternal.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -332,7 +332,7 @@ public bool EnableRaisingEvents
{
string currentMachineName = this.machineName;

if (parent!.ComponentDesignMode)
if (parent?.ComponentDesignMode == true)
this.boolFlags[Flag_monitoring] = value;
else
{
Expand Down Expand Up @@ -377,7 +377,7 @@ public ISynchronizeInvoke? SynchronizingObject
{
get
{
if (this.synchronizingObject == null && parent!.ComponentDesignMode)
if (this.synchronizingObject == null && parent?.ComponentDesignMode == true)
{
IDesignerHost? host = (IDesignerHost?)parent.ComponentGetService(typeof(IDesignerHost));
if (host != null)
Expand Down Expand Up @@ -559,15 +559,17 @@ private void CompletionCallback()
while (i < count)
{
EventLogEntry entry = GetEntryWithOldest(i);
if (onEntryWrittenHandler != null)
EntryWrittenEventHandler? handler = onEntryWrittenHandler;
if (handler is not null)
{
if (this.SynchronizingObject != null && this.SynchronizingObject.InvokeRequired)
ISynchronizeInvoke? synchronizingObject = SynchronizingObject;
if (synchronizingObject is not null && synchronizingObject.InvokeRequired)
{
this.SynchronizingObject.BeginInvoke(this.onEntryWrittenHandler, new object[] { this, new EntryWrittenEventArgs(entry) });
synchronizingObject.BeginInvoke(handler, new object[] { this, new EntryWrittenEventArgs(entry) });
}
else
{
onEntryWrittenHandler(this, new EntryWrittenEventArgs(entry));
handler(this, new EntryWrittenEventArgs(entry));
}
}

Expand Down Expand Up @@ -1173,7 +1175,7 @@ private void StartListening(string currentMachineName, string currentLogName)

private void StartRaisingEvents(string currentMachineName, string currentLogName)
{
if (!boolFlags[Flag_initializing] && !boolFlags[Flag_monitoring] && !parent!.ComponentDesignMode)
if (!boolFlags[Flag_initializing] && !boolFlags[Flag_monitoring] && parent?.ComponentDesignMode != true)
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{
StartListening(currentMachineName, currentLogName);
}
Expand Down Expand Up @@ -1216,7 +1218,7 @@ private void StopListening(/*string currentMachineName,*/ string currentLogName)

private void StopRaisingEvents(/*string currentMachineName,*/ string currentLogName)
{
if (!boolFlags[Flag_initializing] && boolFlags[Flag_monitoring] && !parent!.ComponentDesignMode)
if (!boolFlags[Flag_initializing] && boolFlags[Flag_monitoring] && parent?.ComponentDesignMode != true)
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{
StopListening(currentLogName);
}
Expand Down Expand Up @@ -1360,11 +1362,11 @@ private void InternalWriteEvent(uint eventID, ushort category, EventLogEntryType

for (int i = 0; i < strings.Length; i++)
{
strings[i] ??= string.Empty;
string s = strings[i] ??= string.Empty;

// make sure the strings aren't too long. MSDN says each string has a limit of 32k (32768) characters, but
// experimentation shows that it doesn't like anything larger than 32766
if (strings[i]!.Length > 32766)
if (s.Length > 32766)
throw new ArgumentException(SR.LogEntryTooLong);
}
rawData ??= Array.Empty<byte>();
Expand Down
29 changes: 22 additions & 7 deletions src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogTraceListener.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,11 +85,15 @@ public override void TraceEvent(TraceEventCache? eventCache, string source, Trac
if (Filter != null && !Filter.ShouldTrace(eventCache, source, severity, id, format, args, null, null))
return;

EventLog? eventLog = EventLog;
if (eventLog is null)
return;

EventInstance data = CreateEventInstance(severity, id);

if (args == null || args.Length == 0)
{
EventLog!.WriteEvent(data, format);
eventLog.WriteEvent(data, format);
}
else if (string.IsNullOrEmpty(format))
{
Expand All @@ -99,13 +103,12 @@ public override void TraceEvent(TraceEventCache? eventCache, string source, Trac
strings[i] = args[i]?.ToString();
}

EventLog!.WriteEvent(data, strings);
eventLog.WriteEvent(data, strings);
}
else
{
EventLog!.WriteEvent(data, string.Format(CultureInfo.InvariantCulture, format, args));
eventLog.WriteEvent(data, string.Format(CultureInfo.InvariantCulture, format, args));
}

}

[ComVisible(false)]
Expand All @@ -114,7 +117,11 @@ public override void TraceEvent(TraceEventCache? eventCache, string source, Trac
if (Filter != null && !Filter.ShouldTrace(eventCache, source, severity, id, message, null, null, null))
return;

EventLog!.WriteEvent(CreateEventInstance(severity, id), message);
EventLog? eventLog = EventLog;
if (eventLog is null)
return;

eventLog.WriteEvent(CreateEventInstance(severity, id), message);
}

[ComVisible(false)]
Expand All @@ -123,7 +130,11 @@ public override void TraceData(TraceEventCache? eventCache, string source, Trace
if (Filter != null && !Filter.ShouldTrace(eventCache, source, severity, id, null, null, data, null))
return;

EventLog!.WriteEvent(CreateEventInstance(severity, id), new object?[] { data });
EventLog? eventLog = EventLog;
if (eventLog is null)
return;

eventLog.WriteEvent(CreateEventInstance(severity, id), new object?[] { data });
}

[ComVisible(false)]
Expand All @@ -132,6 +143,10 @@ public override void TraceData(TraceEventCache? eventCache, string source, Trace
if (Filter != null && !Filter.ShouldTrace(eventCache, source, severity, id, null, null, null, data))
return;

EventLog? eventLog = EventLog;
if (eventLog is null)
return;

EventInstance inst = CreateEventInstance(severity, id);

var sb = new StringBuilder();
Expand All @@ -148,7 +163,7 @@ public override void TraceData(TraceEventCache? eventCache, string source, Trace
}
}

EventLog!.WriteEvent(inst, new object[] { sb.ToString() });
eventLog.WriteEvent(inst, new object[] { sb.ToString() });
}

private static EventInstance CreateEventInstance(TraceEventType severity, int id)
Expand Down
11 changes: 11 additions & 0 deletions src/libraries/System.Diagnostics.EventLog/tests/EventLogTraceListenerTests.cs
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Expand Up @@ -28,6 +28,17 @@ public void EventLogConstructor(EventLog eventLog, string expected)
}
}

[ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotNetFramework))]
public void TraceMethods_EventLogNull_NoOp()
{
using var listener = new EventLogTraceListener(eventLog: null);

listener.TraceEvent(null, "source", TraceEventType.Information, 1, "message");
listener.TraceEvent(null, "source", TraceEventType.Information, 1, "{0}", "message");
listener.TraceData(null, "source", TraceEventType.Information, 1, data: (object?)"message");
listener.TraceData(null, "source", TraceEventType.Information, 1, data: new object?[] { "message" });
}

[Fact]
public void StringConstructor()
{
Expand Down
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