Playing around with App-local ICU

CultureIcu.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <PropertyGroup>
    <DebugType>embedded</DebugType>
    <PublishSingleFile>true</PublishSingleFile>
    <UseCurrentRuntimeIdentifier>true</UseCurrentRuntimeIdentifier>
    <SelfContained>false</SelfContained>
    <IncludeNativeLibrariesForSelfExtract>true</IncludeNativeLibrariesForSelfExtract>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.ICU.ICU4C.Runtime" Version="68.2.0.9" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.Globalization;
using System.IO;
using System.Linq;

var output = args.Length == 1 ? new StreamWriter(args[0]) : Console.Out;

// Alternatively, could also use <RuntimeHostConfigurationOption Include="System.Globalization.AppLocalIcu" Value="68" /> in csproj
// See https://docs.microsoft.com/en-us/dotnet/core/extensions/globalization-icu#app-local-icu
output.WriteLine($"DOTNET_SYSTEM_GLOBALIZATION_APPLOCALICU = {Environment.GetEnvironmentVariable("DOTNET_SYSTEM_GLOBALIZATION_APPLOCALICU")}");
output.WriteLine($"Is using ICU?                           = {IsUsingIcu()}");

foreach (var name in new[] { "de-CH", "en-CH", "fr-CH", "it-CH" })
{
    output.WriteLine($"Culture: {name}");
    {
        var culture = new CultureInfo(name, useUserOverride: false);
        output.WriteLine($"  NumberDecimalSeparator   = {UnicodeDescription(culture.NumberFormat.NumberDecimalSeparator)} | NumberGroupSeparator   = {UnicodeDescription(culture.NumberFormat.NumberGroupSeparator)}");
        output.WriteLine($"  CurrencyDecimalSeparator = {UnicodeDescription(culture.NumberFormat.CurrencyDecimalSeparator)} | CurrencyGroupSeparator = {UnicodeDescription(culture.NumberFormat.CurrencyGroupSeparator)}");
        output.WriteLine($"  ShortDatePattern         = {culture.DateTimeFormat.ShortDatePattern}");
    }
}

output.Flush();

static string UnicodeDescription(string value)
{
    return string.Join(" ", value.EnumerateRunes().Select(r => $"{r} (U+{r.Value:X4})"));
}

// From https://docs.microsoft.com/en-us/dotnet/core/extensions/globalization-icu#determine-if-your-app-is-using-icu
static bool IsUsingIcu()
{
    var sortVersion = CultureInfo.InvariantCulture.CompareInfo.Version;
    var bytes = sortVersion.SortId.ToByteArray();
    var version = bytes[3] << 24 | bytes[2] << 16 | bytes[1] << 8 | bytes[0];
    return version != 0 && version == sortVersion.FullVersion;
}