ContextExtensions.cs

using System;
using System.Collections.Generic;
using System.Text;

using Microsoft.EntityFrameworkCore;

namespace DigitalPlatform.LibraryServer.Reporting
{
    public static class ContextExtensions
    {
        // https://www.michaelgmccarthy.com/2016/08/24/entity-framework-addorupdate-is-a-destructive-operation/
        public static void AddOrUpdate(this DbContext ctx, object entity)
        {
            var entry = ctx.Entry(entity);
            switch (entry.State)
            {
                case EntityState.Detached:
                    ctx.Add(entity);
                    break;
                case EntityState.Modified:
                    ctx.Update(entity);
                    break;
                case EntityState.Added:
                    ctx.Add(entity);
                    break;
                case EntityState.Unchanged:
                    //item already in db no need to do anything  
                    break;

                default:
                    throw new ArgumentOutOfRangeException();
            }
        }
    }
}