Compare two model versions

using Speckle.Objects.Data;
using Speckle.Sdk.Models;
using Speckle.Sdk.Models.Extensions;

async Task<Base> LoadVersion(string versionId)
{
    var version = await client.Version.Get(versionId, projectId);
    return await SpeckleBootstrap.Operations.Receive2(
        client.ServerUrl, projectId, version.referencedObject!, account.token,
        onProgressAction: null, cancellationToken: default);
}

static Dictionary<string, DataObject> IndexByAppId(Base root) =>
    root.Flatten()
        .OfType<DataObject>()
        .Where(d => d.applicationId is not null)
        .GroupBy(d => d.applicationId!)
        .ToDictionary(g => g.Key, g => g.First());

var olderRoot = await LoadVersion(olderVersionId);
var newerRoot = await LoadVersion(newerVersionId);

var olderIndex = IndexByAppId(olderRoot);
var newerIndex = IndexByAppId(newerRoot);

var added = newerIndex.Keys.Except(olderIndex.Keys).ToList();
var removed = olderIndex.Keys.Except(newerIndex.Keys).ToList();
var common = olderIndex.Keys.Intersect(newerIndex.Keys).ToList();

var changed = common.Count(id =>
{
    var a = olderIndex[id].properties.GetValueOrDefault("category")?.ToString();
    var b = newerIndex[id].properties.GetValueOrDefault("category")?.ToString();
    return a != b;
});

Console.WriteLine($"Added: {added.Count}, Removed: {removed.Count}, Common: {common.Count}, Category changed: {changed}");