如何让 .NET 程序脱离系统安装的 .NET 运行时独立运行？除了 Self-Contained 之外还有更好方法！谈 dotnetCampus.AppHost 的工作原理

// For apphost and libhost, root_path is expected to be a directory.
// For libhost, it may be empty if app-local search is not desired (e.g. com/ijw/winrt hosts, nethost when no assembly path is specified)
// If a hostfxr exists in root_path, then assume self-contained.
if (root_path.length() > 0 && library_exists_in_dir(root_path, LIBFXR_NAME, out_fxr_path))
{
    trace::info(_X("Resolved fxr [%s]..."), out_fxr_path->c_str());
    out_dotnet_root->assign(root_path);
    return true;
}

// For framework-dependent apps, use DOTNET_ROOT_<ARCH>
pal::string_t default_install_location;
pal::string_t dotnet_root_env_var_name;
if (get_dotnet_root_from_env(&dotnet_root_env_var_name, out_dotnet_root))
{
    trace::info(_X("Using environment variable %s=[%s] as runtime location."), dotnet_root_env_var_name.c_str(), out_dotnet_root->c_str());
}
else
{
    if (pal::get_dotnet_self_registered_dir(&default_install_location) || pal::get_default_installation_dir(&default_install_location))
    {
        trace::info(_X("Using global installation location [%s] as runtime location."), default_install_location.c_str());
        out_dotnet_root->assign(default_install_location);
    }
    else
    {
        trace::error(_X("A fatal error occurred, the default install location cannot be obtained."));
        return false;
    }
}

--  // For framework-dependent apps, use DOTNET_ROOT_<ARCH>
    pal::string_t default_install_location;
    pal::string_t dotnet_root_env_var_name;
++  if (is_dotnet_root_enabled_for_execution(out_dotnet_root))
++  {
++      // For apps that using dotnetCampus.AppHost, use the EMBED_DOTNET_ROOT placeholder.
++      trace::info(_X("Using embedded dotnet_root [%s] as runtime location."), out_dotnet_root->c_str());
++  }
--  if (get_dotnet_root_from_env(&dotnet_root_env_var_name, out_dotnet_root))
++  else if (get_dotnet_root_from_env(&dotnet_root_env_var_name, out_dotnet_root))
    {
++      // For framework-dependent apps, use DOTNET_ROOT_<ARCH>
        trace::info(_X("Using environment variable %s=[%s] as runtime location."), dotnet_root_env_var_name.c_str(), out_dotnet_root->c_str());
    }
    else
    {
        if (pal::get_dotnet_self_registered_dir(&default_install_location) || pal::get_default_installation_dir(&default_install_location))
        {
            trace::info(_X("Using global installation location [%s] as runtime location."), default_install_location.c_str());
            out_dotnet_root->assign(default_install_location);
        }
        else
        {
            trace::error(_X("A fatal error occurred, the default install location cannot be obtained."));
            return false;
        }
    }

#if defined(FEATURE_APPHOST) || defined(FEATURE_LIBHOST)
#define EMBED_DOTNET_ROOT_HI_PART_UTF8 "622e5d2d0f48bd3448f713291ed3f86d" // SHA-256 of "DOTNET_ROOT" in UTF-8
#define EMBED_DOTNET_ROOT_LO_PART_UTF8 "f2f05ca222e95084f222207c5c348eea"
#define EMBED_DOTNET_ROOT_FULL_UTF8    (EMBED_DOTNET_ROOT_HI_PART_UTF8 EMBED_DOTNET_ROOT_LO_PART_UTF8) // NUL terminated

bool is_dotnet_root_enabled_for_execution(pal::string_t* dotnet_root)
{
    constexpr int EMBED_SZ = sizeof(EMBED_DOTNET_ROOT_FULL_UTF8) / sizeof(EMBED_DOTNET_ROOT_FULL_UTF8[0]);
    constexpr int EMBED_MAX = (EMBED_SZ > 1025 ? EMBED_SZ : 1025); // 1024 DLL name length, 1 NUL

    // Contains the EMBED_DOTNET_ROOT_FULL_UTF8 value at compile time or the managed DLL name replaced by "dotnet build".
    // Must not be 'const' because std::string(&embed[0]) below would bind to a const string ctor plus length
    // where length is determined at compile time (=64) instead of the actual length of the string at runtime.
    static char embed[EMBED_MAX] = EMBED_DOTNET_ROOT_FULL_UTF8;     // series of NULs followed by embed hash string

    static const char hi_part[] = EMBED_DOTNET_ROOT_HI_PART_UTF8;
    static const char lo_part[] = EMBED_DOTNET_ROOT_LO_PART_UTF8;

    if (!pal::clr_palstring(embed, dotnet_root))
    {
        trace::error(_X("The dotnet_root value could not be retrieved from the executable image."));
        return false;
    }

    // Since the single static string is replaced by editing the executable, a reference string is needed to do the compare.
    // So use two parts of the string that will be unaffected by the edit.
    size_t hi_len = (sizeof(hi_part) / sizeof(hi_part[0])) - 1;
    size_t lo_len = (sizeof(lo_part) / sizeof(lo_part[0])) - 1;

    std::string binding(&embed[0]);
    if ((binding.size() >= (hi_len + lo_len)) &&
        binding.compare(0, hi_len, &hi_part[0]) == 0 &&
        binding.compare(hi_len, lo_len, &lo_part[0]) == 0)
    {
        trace::info(_X("This executable does not binding to dotnet_root yet. The binding value is: '%s'"), dotnet_root->c_str());
        return false;
    }

    trace::info(_X("The dotnet_root binding to this executable is: '%s'"), dotnet_root->c_str());
    if (pal::realpath(dotnet_root))
    {
        return true;
    }
    trace::info(_X("Did not find binded dotnet_root directory: '%s'"), dotnet_root->c_str());
    return false;
}
#endif // FEATURE_APPHOST

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

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFrameworks>net6.0;net5.0;net45</TargetFrameworks>
    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
    <GenerateDocumentationFile>true</GenerateDocumentationFile>
    <RootNamespace>dotnetCampus.AppHosting</RootNamespace>
    <IncludeBuildOutput>false</IncludeBuildOutput>
  </PropertyGroup>

  <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">
    <PackageReference Include="dotnetCampus.CommandLine.Source" Version="3.3.0" PrivateAssets="All" />
    <PackageReference Include="dotnetCampus.MSBuildUtils.Source" Version="1.1.0" PrivateAssets="All" />
  </ItemGroup>

  <ItemGroup Condition="'$(TargetFramework)' != 'net6.0'">
    <Compile Remove="**\*.cs" />
    <Compile Include="Program.cs" />
  </ItemGroup>

  <!-- 引入包文件用于打包。 -->
  <Target Name="_IncludeAllDependencies" BeforeTargets="_GetPackageFiles">
    <ItemGroup>
      <None Include="Assets\build\Build.props" Pack="True" PackagePath="build\$(PackageId).props" />
      <None Include="Assets\build\Build.targets" Pack="True" PackagePath="build\$(PackageId).targets" />
      <None Include="Assets\template\**" Pack="True" PackagePath="template" />
      <None Include="$(OutputPath)net6.0\**" Pack="True" PackagePath="tools" />
    </ItemGroup>
  </Target>