Database operation expected to affect 1 row(s) but actually affected 0 row(s)

Make sure in your repository function InsertAsync you are not calling AddAsync unless your are using the Microsoft.EntityFrameworkCore.Metadata.SqlServerValueGenerationStrategy.SequenceHiLo generator. AS NOTED IN the Docs. AddAsync

I had a similar problem. I used EF Core. I was helped by the following change for my code.

context.Entry(user).State = EntityState.Added; // added row
this.context.Users.Add(user);
this.context.SaveChanges();

UPD: Sorry, problem has been solved by adding a Identity attribute for User.Id

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]