EF Core 更新现有实体

Question

I'm using EF Core and .NET 6 and I would like to essentially upsert an entity to a table - a fairly simple ask.

I have the following code:

var countries = GetCountries();

using (var scope = scopeFactory.CreateScope())
{
    var dbContext = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();

    foreach (var c in countries)
    {
        // check if the country already exists.
        var exists = dbContext.Countries.Where(d => d.Id == c.Id).FirstOrDefault();

        // if already exists - update (rather than add).
        if (exists != null) 
        {
            exists.Name = c.Name;
            exists.DisplayName = c.DisplayName;
            ... // omitted other prop updates.

            dbContext.Countries.Update(exists);
        } 
        else
        {
            dbContext.Countries.Add(c);
        }
    }

    await dbContext.SaveChangesAsync();
}

I was wondering - is there was a more efficient way to update without manually looking up then updating (it's not very performant).

Preferably, I was hoping there was a Merge method in EF Core but can't find anything useful (that's free...). Rather than doing the manual lookup and update in this way.

I'm probably missing something very obvious here - thanks for any pointers in advance!

Answer 1

EF Core do not have Merge , or similar for Upsert. You can improve performance of your query by selecting existng items in one batch. Also you do not need to call Update , just change properties.

var countries = GetCountries();

using (var scope = scopeFactory.CreateScope())
{
    var dbContext = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();

    var countyIds = countries.Select(c => c.Id);
    var existing = (await dbContext.Countries.Where(d => countyIds.Contains(d.Id))
        .ToListAsync())
        .ToDictionary(c => c.Id);

    foreach (var c in countries)
    {
        // check if the country already exists.

        if (existing.TryGetValue(c.Id, out var toUpdate))
        {
            // if already exists - update (rather than add).
            toUpdate.Name = c.Name;
            toUpdate.DisplayName = c.DisplayName;
            ... // omitted other prop updates.
        } 
        else
        {
            dbContext.Countries.Add(c);
        }
    }

    await dbContext.SaveChangesAsync();
}

Answer 2

public void InsertOrUpdate(Entity entity) 
{ 
    using (var context = new dbContext.Countries()) 
    { 
        context.Entry(entity).State = entity.Id == 0 ? 
                                   EntityState.Added : 
                                   EntityState.Modified; 

        context.SaveChanges(); 
    } 
}