public async Task NullifyExpertRelation(Func <IQueryable <Lead>, IQueryable <Lead> > queryBuilder)
{
using (DbContext context = DbContextManager.BuildNewContext())
{
List <Lead> leads = EntityFrameworkQueryableExtensions.AsNoTracking(queryBuilder(context.Set <Lead>())).ToList();
foreach (var lead in leads)
{
Lead stubLead = new Lead()
{
Id = lead.Id, ExpertId = null
};
context.Set <Lead>().Attach(stubLead);
context.Entry(stubLead).Property(x => x.ExpertId).IsModified = true;
}
await context.SaveChangesAsync();
}
}