efcore: Exception when inserting multiple rows into the same table on SQL Server

Include your code

Beginning with EF Core 7.0 rc2 when a database entity is generated through a projection and then saved as a new entity, EF Core will throw exception due to “temporary value” of Id property.

Workaround: set Id to default before saving.

Pre-7.0 this was not necessary. If this is expected, it would be nice to add to https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-7.0/breaking-changes

var digests = await _context.Users
    .Select(u => new DailyDigest
    {
        User = u,
        TimeCreatedUtc = utcNow,
    })
    .ToListAsync();

foreach (var digest in digests)
{
    // next line is necessary in 7.0 rc2, was not necessary in 6.0 and below (down to 1.0 ?)
    // digest.Id = default;

    _context.DailyDigests.Add(digest);
}

await _context.SaveChangesAsync();

Include stack traces

System.InvalidOperationException: The property 'DailyDigest.Id' has a temporary value while attempting to change the entity's state to 'Unchanged'. Either set a permanent value explicitly, or ensure that the database is configured to generate values for this property.
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState oldState, EntityState newState, Boolean acceptChanges, Boolean modifyProperties)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean modifyProperties, Nullable`1 forceStateWhenUnknownKey, Nullable`1 fallbackState)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.AcceptChanges()
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.AcceptAllChanges(IReadOnlyList`1 changedEntries)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.<>c__DisplayClass30_0`2.<<ExecuteAsync>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteImplementationAsync[TState,TResult](Func`4 operation, Func`4 verifySucceeded, TState state, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteImplementationAsync[TState,TResult](Func`4 operation, Func`4 verifySucceeded, TState state, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)

Include provider and version information

EF Core version: 7.0 rc2 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: 7.0 rc2 Operating system: Win11 IDE: Visual Studio 2022 17.4