WASM Globalization Icu

In WASM applications when globalization invariant mode is switched off, internalization data file is loaded. There are four basic types of these files:

• icudt.dat - full data
• icudt_EFIGS.dat - data for locales: "en-*", "fr-FR", "es-ES", "it-IT", and "de-DE".
• icudt_CJK.dat - for locales: "en" "ja", "ko", and "zh".
• icudt_no_CJK.dat - all locales from icudt.dat, excluding "ja", "ko", and "zh".

Wasm Console, Wasm Browser

We can specify the file we want to load, e.g. icudt_no_CJK.dat by adding to .csproj:

<WasmIcuDataFileName>icudt_no_CJK.dat</WasmIcuDataFileName>

Only one value for WasmIcuDataFileName can be set. It can also be a custom file, created by the developer. To create a custom ICU file, see Custom ICU section below. If no WasmIcuDataFileName was specified, the application's culture will be checked and the corresponding file will be loaded, e.g. for en-US file icudt_EFIGS.dat, and for zh-CN - icudt_CJK.dat.

Custom ICU

The easiest way to build ICU is to open https://github.com/dotnet/icu/ it in Codespaces. See files in https://github.com/dotnet/icu/tree/dotnet/main/icu-filters, and read https://unicode-org.github.io/icu/userguide/icu_data/buildtool.html#locale-slicing. Build your own filter or edit the existing file. We advise to edit the filters only by adding/removing locales from the localeFilter/includelist to avoid removing important data. We recommend not to remove "en-US" locale from the localeFilter/includelist because it is used as a fallback. Removing it for when

• <PredefinedCulturesOnly>true</PredefinedCulturesOnly>: results in Encountered infinite recursion while looking for resource in System.Private.Corelib. exception
• when predefined cultures only is not set: results in resolving data from ICU's root.txt files, e.g. CultureInfo.DateTimeFormat.GetDayName(DateTime.Today.DayOfWeek) will return an abbreviated form: Mon instead of Monday. Removing specific feature data might result in an exception that starts with [CultureData.IcuGetLocaleInfo(LocaleStringData)] Failed. It means you removed data necessary to extract basic information about the locale.

In the file eng/icu.mk, you can choose what filters to build. Choose the platform:

Building for Browser:

• For prerequisites run .devcontainer/postCreateCommand.sh (it is run automatically on creation if using Codespaces)
• Building:

  ./build.sh /p:TargetOS=Browser /p:TargetArchitecture=wasm
  

  Output is located in artifacts/bin/icu-browser-wasm.

Building for Mobiles:

• For prerequisites run:

  export ANDROID_NDK_ROOT=$PWD/artifacts/ndk/
  mkdir  $ANDROID_NDK_ROOT
  wget https://dl.google.com/android/repository/android-ndk-r25b-linux.zip
  unzip android-ndk-r25b-linux.zip -d $ANDROID_NDK_ROOT
  rm android-ndk-r25b-linux.zip
  mv $ANDROID_NDK_ROOT/*/* $ANDROID_NDK_ROOT
  rmdir $ANDROID_NDK_ROOT/android-ndk-r25b
  

• Building:

 ./build.sh /p:TargetOS=Android /p:TargetArchitecture=x64

Output from both builds will be located in subdirectories of artifacts/bin. Copy the generated .dat files to your project location and provide the path to it in the .csproj, e.g.:

<!-- relative path -->
<WasmIcuDataFileName>icudt_custom.dat</WasmIcuDataFileName>

<!-- OR absolute -->
<WasmIcuDataFileName>$(MSBuildThisFileDirectory)icudt_custom.dat</WasmIcuDataFileName>

Blazor

In Blazor we are loading the file based on the applications's culture. To force the full data to be loaded, add this to your .csproj:

<BlazorWebAssemblyLoadAllGlobalizationData>true</BlazorWebAssemblyLoadAllGlobalizationData>

Custom files loading for Blazor is supported only for files with names starting with icudt, e.g. icudt_custom.dat. To load the file use BlazorIcuDataFileName property with either a path relative to your project or a full path, like for WasmIcuDataFileName.