Upsert in generic EF core repository

Question

While it feels that this question should have been answered many times already, I can not find anything useful (except for BulkInsert addons which I'd like to avoid)

        public virtual void AddRange(ICollection<T> entries)
        {
            _context.Set<T>().AddRange(entries);
        }

        public virtual void UpdateRange(ICollection<T> entries)
        {
            _context.Set<T>().UpdateRange(entries);
        }

So how to combine these 2 methods together? T is a class and has a key "Id" property (or it can have other composite key, thus I want this solution to be truly generic), but I don't want to make an interface out of it (to check if equals to 0 to mark entry as Added, Modified otherwise) as it complicates design.

Answer 1

Since you are wanting to do a 'BulkInsert' you can use the UpdateRange(IEnumerable items) method which is provided by the DbContext. So, in your case you would create a new method inside your repository and do:

public void Upsert<T>(IEnumerable<T> items)
{

    _context.DbSet<T>.UpdateRange(items);
    _context.SaveChanges(); // persist to db
}

then you can use it like this (pseudo code)

var myRepository = new repository<Onion>(_context);
var entities = _context.Onions;
foreach(var entity in entities){
   entity.Layers = 8
}
myRepository.Upsert(entities);
// you could do SaveChanges() here too.

If you want to do something custom, you can use the following, but it is not as efficient as UpdateRange because it does a query for each item in the collection passed in.

public void AddOrUpdateRange<T>(ICollection<T> items)
{
    foreach (var item in items)
    {
        var existingItem = _context.Set<T>().Find(item.Id);
        if (existingItem != null)
        {
            _context.Entry(existingItem).CurrentValues.SetValues(item);
        }
        else
        {
            _context.Set<T>().Add(item);
        }
    }
    _context.SaveChanges();
}

Answer 2

All good conversations/comments. I have a similar scenario of Upsert operation but i had to have my repo handle that. I tried to modify it to match your need and came up like below.

// Business layer
public async Task<bool> UpsertOnions(IEnumerable<Onions> list)
{
    var existingRecs = (await _onionRepo.Get(existing => list.Select(model => model.Pk).Contains(existing.Pk)).ToList();
    if (!existingRecs.Any())
        return await _onionRepo.UpdateRange(existingRecs);
    
    var allNetNew = list.Except(existingRecs);
    return await _onionRepo.AddRange(allNetNew);
}

// Repo implementation
public async Task<bool> UpdateRange(IEnumerable<T> list)
{
    _dbSet.UpdateRange(list);
    // manage to handle your own here like return values etc. 
    // call SaveChanges()
    return true; // change to your own implementation
}

public async Task<bool> AddRange(IEnumerable<T> list)
{
    _dbSet.AddRange(list);
    // manage to handle your own here like return values etc. 
    // call SaveChanges()
    return true; // change to your own implementation
}

Here, i go with my assumption that when you get your data and map to your desired data model, your external data with its own openId should get associated to the Pk field of the model.

I am also trying to speak in general aspect without specific Database provider in mind. Like, Postgres or SQL, where your datamodel would only decorate your Pk property as [Key].