Does EF upsert have to be done manually?

Question

I want to upsert reference members of an existing entity.

Do I have to write specific code for the upsert?

meaning: I have to check if I\'m handling an existing

Answer 1

To avoid the overhead of a query and then insert, or throwing exceptions, you can take advantage of the underlying database support for merges or upserts.

This nuget package does the job pretty well: https://www.nuget.org/packages/FlexLabs.EntityFrameworkCore.Upsert/

Github: https://github.com/artiomchi/FlexLabs.Upsert

Example:

DataContext.DailyVisits
    .Upsert(new DailyVisit
    {
        // new entity path
        UserID = userID,
        Date = DateTime.UtcNow.Date,
        Visits = 1,
    })
    // duplicate checking fields
    .On(v => new { v.UserID, v.Date })
    .WhenMatched((old, @new) => new DailyVisit
    {
        // merge / upsert path
        Visits = old.Visits + 1,
    })
    .RunAsync();

The underlying generated sql does a proper upsert. This command runs right away and does not use change tracking, so that is one limitation.