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The MSBuild properties and items described in this article influence the behavior of trimmed, self-contained deployments. Some of the options mention ILLink, which is the name of the underlying tool that implements trimming. For more information about the underlying tool, see the Trimmer documentation.
Trimming with PublishTrimmed was introduced in .NET Core 3.0. The other options are available in .NET 5 and later versions.
Enable trimming
<PublishTrimmed>true</PublishTrimmed>Enable trimming during publish. This setting also turns off trim-incompatible features and enables trim analysis during build. In .NET 8 and later apps, this setting also enables the configuration binding and request delegate source generators.
Note
If you specify trimming as enabled from the command line, your debugging experience will differ and you might encounter additional bugs in the final product.
Place this setting in the project file to ensure that the setting applies during dotnet build, not just dotnet publish.
This setting also enables the trim-compatibility Roslyn analyzer and disables features that are incompatible with trimming.
Roslyn analyzer
Setting PublishTrimmed in .NET 6+ also enables a Roslyn analyzer that shows a limited set of analysis warnings. You can also enable or disable the analyzer independently of PublishTrimmed.
<EnableTrimAnalyzer>true</EnableTrimAnalyzer>Enable a Roslyn analyzer for a subset of trim analysis warnings.
Suppress warnings
You can suppress individual warning codes using the usual MSBuild properties respected by the toolchain, including NoWarn, WarningsAsErrors, WarningsNotAsErrors, and TreatWarningsAsErrors. There's an additional option that controls the ILLink warn-as-error behavior independently:
<ILLinkTreatWarningsAsErrors>false</ILLinkTreatWarningsAsErrors>Don't treat ILLink warnings as errors. This might be useful to avoid turning trim analysis warnings into errors when treating compiler warnings as errors globally.
Show detailed warnings
In .NET 6+, trim analysis produces at most one warning for each assembly that comes from a PackageReference, indicating that the assembly's internals are not compatible with trimming. You can also show individual warnings for all assemblies:
<TrimmerSingleWarn>false</TrimmerSingleWarn>Show all detailed warnings, instead of collapsing them to a single warning per assembly.
Remove symbols
Symbols are usually trimmed to match the trimmed assemblies. You can also remove all symbols:
<TrimmerRemoveSymbols>true</TrimmerRemoveSymbols>Remove symbols from the trimmed application, including embedded PDBs and separate PDB files. This applies to both the application code and any dependencies that come with symbols.
The SDK also makes it possible to disable debugger support using the property DebuggerSupport. When debugger support is disabled, trimming removes symbols automatically (TrimmerRemoveSymbols will default to true).
Trim framework library features
Several feature areas of the framework libraries come with trimmer directives that make it possible to remove the code for disabled features.
| MSBuild property | Description |
|---|---|
AutoreleasePoolSupport |
When set to false, removes code that creates autorelease pools on supported platforms. false is the default for the .NET SDK. |
DebuggerSupport |
When set to false, removes code that enables better debugging experiences. This setting also removes symbols. |
EnableUnsafeBinaryFormatterSerialization |
When set to false, removes BinaryFormatter serialization support. For more information, see BinaryFormatter serialization methods are obsolete and In-box BinaryFormatter implementation removed and always throws. |
EnableUnsafeUTF7Encoding |
When set to false, removes insecure UTF-7 encoding code. For more information, see UTF-7 code paths are obsolete. |
EventSourceSupport |
When set to false, removes EventSource-related code and logic. |
HttpActivityPropagationSupport |
When set to false, removes code related to diagnostics support for System.Net.Http. |
InvariantGlobalization |
When set to true, removes globalization-specific code and data. For more information, see Invariant mode. |
MetadataUpdaterSupport |
When set to false, removes metadata update–specific logic related to hot reload. |
MetricsSupport |
When set to false, removes support for System.Diagnostics.Metrics instrumentation. |
StackTraceSupport (.NET 8+) |
When set to false, removes support for generating stack traces (for example, Environment.StackTrace or Exception.ToString) by the runtime. The amount of information that is removed from stack trace strings might depend on other deployment options. This option does not affect stack traces generated by debuggers. |
UseNativeHttpHandler |
When set to true, uses the default platform implementation of HttpMessageHandler for Android and iOS and removes the managed implementation. |
UseSystemResourceKeys |
When set to true, strips exception messages for System.* assemblies. When an exception is thrown from a System.* assembly, the message is a simplified resource ID instead of the full message. |
XmlResolverIsNetworkingEnabledByDefault (.NET 8+) |
When set to false, removes support for resolving non-file URLs in System.Xml. Only file-system resolving is supported. |
These properties cause the related code to be trimmed and also disable features via the runtimeconfig file. For more information about these properties, including the corresponding runtimeconfig options, see feature switches. Some SDKs might have default values for these properties.
Framework features disabled when trimming
The following features are incompatible with trimming because they require code that's not statically referenced. These features are disabled by default in trimmed apps.
Warning
Enable these features at your own risk. They are likely to break trimmed apps without extra work to preserve the dynamically referenced code.
<BuiltInComInteropSupport>Built-in COM support is disabled.
<CustomResourceTypesSupport>Use of custom resource types isn't supported. ResourceManager code paths that use reflection for custom resource types are trimmed.
<EnableCppCLIHostActivation>C++/CLI host activation is disabled.
<EnableUnsafeBinaryFormatterInDesigntimeLicenseContextSerialization>DesigntimeLicenseContextSerializer use of
BinaryFormatterserialization is disabled.<StartupHookSupport>Running code before
MainwithDOTNET_STARTUP_HOOKSisn't supported. For more information, see host startup hook.
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