The linking process in Xamarin is a crucial optimization step that helps reduce the size of the final application by removing unused code from the compiled assemblies. This process is particularly important for mobile applications where minimizing the app size can lead to faster downloads and better performance.
Overview of the Linking Process
Purpose: The primary goal of the linker is to strip out any code that is not used in the application. This includes methods, fields, and even entire assemblies that are not referenced anywhere in the code. By doing so, the linker helps in reducing the size of the final APK (Android) or IPA (iOS) file.
Linker Options: Xamarin provides several options for configuring the linker:
None/Don’t Link: The linker does not remove any code, and everything is included in the final package.
SDK Assemblies Only: Only the base class libraries and framework assemblies are linked. This is the default setting for release builds and is generally the safest option.
SDK and User Assemblies: All assemblies, including user code, are linked. This option can significantly reduce the app size but may require additional configuration to prevent the removal of necessary code.
Configuration: The linker can be configured through the project properties in Visual Studio:
For Android, the linker settings can be found under Properties > Android Options.
For iOS, the settings are available under Properties > iOS Build.
Handling Common Issues
The linker can sometimes be too aggressive, removing code that is actually needed at runtime, especially if the code is accessed via reflection or dynamically instantiated. To handle such cases, developers can use several techniques:
Custom Linker Configuration: Developers can create an XML file that specifies which assemblies, types, methods, and fields should not be removed by the linker. This file is then added to the project with the build action set to LinkDescription[1][3].
Preserve Attribute: Xamarin provides a Preserve attribute that can be applied to classes, methods, or fields to ensure they are not removed by the linker. This attribute can be used in both Android and iOS projects[3][11].
LinkerPleaseInclude Class: Another technique is to create a class that references the methods and properties you want to keep. This class is not called anywhere in the code but serves as a hint to the linker that these methods and properties are used[3][11].
Skipping Assemblies: If entire assemblies need to be preserved, developers can ...
