Upsert Dictionary in MongoDb

Question

To the best of my knowledge the mongodb knows Dictionary as an object, and it can't do any operation related to array. I changed the serialization and tried with various type of dictionary's serialization. but there is no chance.
so I load my field(dictionary)(whole of them) into memory, update it and set it back to mongodb.
Is there any way to upsert dictionary in mongodb with c# driver?

---

my document type:

public class Site
    {
        public string Id { get; set; }
        //[BsonDictionaryOptions(DictionaryRepresentation.ArrayOfDocuments)]
        public Dictionary<string,string> Properties { get; set; }
    }

my update operation:

public ServiceResult UpdateProperties(string id, Dictionary<string,string> properties)
        {
            var baseList = Collection.Find(m => m.Id == id)
                .Project(s => s.Properties)
                .FirstOrDefault();

            if (baseList == null)
            {
                baseList = properties;
            }
            else
            {
                baseList.Upsert(properties); //update,insert dic by new one
            }

            var filter = Builders<Site>.Filter
                .Eq(m => m.Id, id);

            var update = Builders<Site>.Update
                .Set(m => m.Properties, baseList);

            try
            {
                Collection.UpdateOne(filter, update);

                return ServiceResult.Okay(Messages.ItemUpdated);

            }
            catch (Exception ex)
            {
                return ServiceResult.Exception(ex);
            }    
        }

I really appreciate any help you can provide.

---

disambiguation :

public static class DictionaryExtensions
    {
        public static void Upsert<TKey, TValue>(this Dictionary<TKey, TValue> source, 
                                          Dictionary<TKey, TValue> newOne)
        {
            foreach (var item in newOne)
            {
                source[item.Key] = item.Value;
            }
        }
    }

Answer 1

You could go through all properties you want to update/insert and do it for each property:

UpdateDefinition<Site> upsert = null;
if (properties.Any())
{
    var firstprop = properties.First();
    upsert = Builders<Site>.Update.Set(nameof(Site.Properties) + "." + firstprop.Key, 
                               firstprop.Value);

    foreach (var updateVal in properties.Skip(1))
    {
        upsert = upsert.Set(nameof(Site.Properties) + "." + updateVal.Key, 
                                          updateVal.Value);
    }

    collection.UpdateOne(r => r.Id == "YourId", upsert, 
                                               new UpdateOptions { IsUpsert = true });
}

Previous version of the answer, with multiple updates:

foreach (var updateVal in properties)
{
    collection.UpdateOne(r => r.Id == "YourId", 
        Builders<Site>.Update.Set( nameof(Site.Properties)+ "." + updateVal.Key, 
                                   updateVal.Value), 
                                   new UpdateOptions { IsUpsert = true});
}

Note, that will just add new Key/Values or update existing, this won't remove anything.