🏁 Script executed:

#!/bin/bash
# Find AppDomainFixedOutput attribute definition
echo "=== AppDomainFixedOutput definition ==="
fd -e cs . src/ --exec rg -l "AppDomainFixedOutput" {} \; | head -20

echo -e "\n=== AppDomainFixedOutput attribute definition ==="
rg -A10 "class AppDomainFixedOutputAttribute" --type=cs

Repository: NLog/NLog

Length of output: 162

🏁 Script executed:

#!/bin/bash
# Check all wrapper classes and their attributes
echo "=== Wrapper classes with attributes ==="
cd src/NLog/LayoutRenderers/Wrappers
for file in *.cs; do
  echo "=== $file ==="
  head -60 "$file" | rg -B2 "^\s*\[.*\]|class.*Wrapper"
done

Repository: NLog/NLog

Length of output: 162

🏁 Script executed:

#!/bin/bash
# Check WhenEmptyLayoutRendererWrapper in detail
echo "=== WhenEmptyLayoutRendererWrapper class structure ==="
cat -n src/NLog/LayoutRenderers/Wrappers/WhenEmptyLayoutRendererWrapper.cs | head -130

Repository: NLog/NLog

Length of output: 162

🌐 Web query:

NLog AppDomainFixedOutput attribute semantics layout renderer

💡 Result:

Short answer — AppDomainFixedOutputAttribute marks a Layout or LayoutRenderer whose rendered value is constant for the lifetime of the current AppDomain (so it never changes between log events). NLog can then evaluate/cache that value once (at init/config time or when capturing state) instead of rendering it per-log-event on the logging thread. Without this attribute NLog will render the layout on the main/logging thread every time. [1]

Notes:

• It’s different from ThreadAgnostic/ThreadAgnosticImmutable (which say the renderer is safe to run on any thread); AppDomainFixedOutput specifically signals the value is fixed for the AppDomain lifetime and may be precomputed/cached. [1]

Source: NLog API docs (AppDomainFixedOutputAttribute description). [1]

References
[1] NLog API documentation — NLog.Config namespace (AppDomainFixedOutputAttribute).

🌐 Web query:

NLog WhenEmptyLayoutRendererWrapper optimization performance

💡 Result:

Short answer: NLog already added a specific optimization for WhenEmptyLayoutRendererWrapper (IStringValueRenderer logic) in recent releases — upgrade to a current NLog 5.x/5.5+ to get that improvement. Also follow general layout-renderer performance guidance (mark thread-agnostic where possible, avoid heavy renderers like callsite/stacktrace, and use Async/Buffering wrappers). [1][2][3]

Sources

• NLog 5.5.0 release notes (calls out "WhenEmptyLayoutRendererWrapper - Optimize IStringValueRenderer Logic"). [1]
• NLog docs: WhenEmptyLayoutRendererWrapper reference. [2]
• NLog performance guidance (layout-renderer optimization, ThreadAgnostic notes). [3]

🌐 Web query:

NLog layout renderer wrapper AppDomainFixedOutput conditional output

💡 Result:

You can conditionally render the AppDomain (or any layout) using NLog's wrapper layout renderers (e.g. ${when}, ${onexception}, ${whenEmpty}). The AppDomain renderer is ${appdomain}. Example — render short AppDomain name only when logger == "MyLogger":

${when:when=logger=='MyLogger':inner=${appdomain:format=Short}}

Notes:

• Use ${onexception:inner=...} to output only on exceptions.
• Use ${whenEmpty:inner=...:else=...} to provide fallback text when inner is empty.
  Docs: NLog wrapper renderers list, AppDomain renderer, and When wrapper. [1][2][3]

Sources
[1] NLog.LayoutRenderers.Wrappers (wrapper list).
[2] AppDomainLayoutRenderer documentation.
[3] WhenLayoutRendererWrapper (conditional wrapper).