Does MSBuild have a property for getting the root folder of the .NET SDK itself.

[AraHaan]

Currently I have a build tasks assembly that uses complex logic to try to resolve the currently used version of the .NET SDK but it has a few issues:

• if both x86 and x64 .NET SDKs are installed it could randomly select the x86 one when the x64 version should be preferred unless the user is currently using the 64 bit version.
  • I personally think a way to directly get it from MSBuild is much better for both performance and simplicity just like there is a way to get the current .NET SDK RID (RuntimeIdentifier).
    • Build tasks targeting netstandard2.0 could benefit from this because RuntimeInformation.RuntimeIdentifier does not exist there for good reason (It does not exist in .NET Framework).
• The logic for getting this correct in build tasks is way too complex than need be and has to account not only windows but also MacOS and Linux, and all other systems that might have different paths.
  • The logic does not handle manual .NET SDK installs in custom locations, vs getting it from MSBuild directly would handle it for free.

As such I am asking here if it is currently possible to get the values that this function would return in a much more accurate way from any existing msbuild properties from the .NET SDK today (Code to this taken from a console application targeting .NET 8, but my build tasks uses a similar logic):

    private static string GetDotNetSdkLocation(string runtimeIdentifier)
    {
        var knownDotNetLocations = (OperatingSystem.IsWindows(), OperatingSystem.IsLinux(), OperatingSystem.IsMacOS()) switch
        {
            (true, false, false) =>
            [
                Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86),
                    "dotnet",
                    "dotnet.exe"),
                Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles),
                    "dotnet",
                    "dotnet.exe"),
            ],
            (false, false, true) =>
            [
                "/usr/local/share/dotnet/dotnet",
            ],
            (false, true, false) =>
            [
                Path.Combine(
                    Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
                    "share",
                    "dotnet",
                    "dotnet")
            ],
            _ => Array.Empty<string>(),
        };
        var sdkRoot = string.Empty;
        var envSdkRoot = Environment.GetEnvironmentVariable("DOTNET_ROOT");
        if (envSdkRoot is not null && Directory.Exists(envSdkRoot))
        {
            sdkRoot = envSdkRoot;
        }

        if (string.IsNullOrEmpty(sdkRoot) || !Directory.Exists(sdkRoot))
        {
            foreach (var loc in knownDotNetLocations)
            {
                // for x64/arm64 versions of the .NET SDK
                if (OperatingSystem.IsWindows()
                    && (RuntimeInformation.OSArchitecture == Architecture.X64
                    || RuntimeInformation.OSArchitecture == Architecture.Arm64)
                    && loc.Contains("Program Files (x86)")
                    && runtimeIdentifier.Equals(RuntimeInformation.RuntimeIdentifier, StringComparison.Ordinal))
                {
                    // we need the 64 bit sdk location (if installed) instead.
                    var loc2 = knownDotNetLocations[Array.IndexOf(knownDotNetLocations, loc) + 1];
                    if (File.Exists(loc2))
                    {
                        var dotnet = new FileInfo(loc2);
                        var sdkDir = dotnet.Directory;
                        if (sdkDir is not null)
                        {
                            sdkRoot = sdkDir.FullName;
                        }

                        break;
                    }
                }

                if (File.Exists(loc))
                {
                    var dotnet = new FileInfo(loc);
                    var sdkDir = dotnet.Directory;
                    if (sdkDir is not null)
                    {
                        sdkRoot = sdkDir.FullName;
                    }

                    break;
                }
            }
        }

        return sdkRoot;
    }