efcoretrackedissueone.cs

public class UserSettingsService : IUserSettingsService
{
    private readonly StockNotificationContext _dbContext;

    public UserSettingsService(StockNotificationContext dbContext)
    {
        _dbContext = dbContext;
    }
    
    public async Task UpdateUserSellerPreferences(string username, IEnumerable<int> sellerIds)
    {
        var allSellerIds = await _dbContext.tblSellers.Select(x => x.Id).ToListAsync();

        var currentExclusions = await _dbContext.tblExcludedSellers.Where(x => x.Username == username).Select(x => x.SellerId).ToListAsync();

        // Determine insertions and removals based on provided ids and what's currently in db
        var correctExclusions = allSellerIds.Except(sellerIds);

        var removals = currentExclusions.Except(correctExclusions)
            .Select(x => new tblExcludedSellers
            {
                Username = username,
                SellerId = x,
            });

        var insertions = correctExclusions.Except(currentExclusions)
            .Select(x => new tblExcludedSellers
            {
                Username = username,
                SellerId = x,
            });

        _dbContext.tblExcludedSellers.AddRange(insertions);
        _dbContext.tblExcludedSellers.RemoveRange(removals);
        await _dbContext.SaveChangesAsync();
    }