What is the proper way to update Many To Many with EF?

Question

I am curious as to what the proper way to update a list of entities at one time is.

    public ActionWas Update(IEnumerable<surcharge_template> templates)
    {
        try
        {
            var templatesToBeUpdated = _context.surcharge_template.Where(x => templates.Select(template => template.st_key).Contains(x.st_key));
           //Right here I need to map all of the differences from the original templates
           //to the new templates
            _context.Entry(templatesToBeUpdated).State = EntityState.Modified;
        }
        catch (Exception ex)
        {
            return _exceptionConverter.Convert(ex);
        }
        _context.SaveChanges();
        return ActionWas.Successsful;
    }

I put a comment at the point where I am not sure the way to handle this. I get the original templates from the database and then I need to map them, then commit and save.

So what is the proper way to map them?

UPDATE:

I would like to do this with EF only making one call to the database. Enumerating the list would cause multipe update statements.

Answer 1

You don't need to map the current entity. You can use a syntax like the SQL Update instead.

Use EntityFramework.Extended

//update all tasks with status of 1 to status of 2
context.Templates.Update(
    t => t.StatusId == 1, 
    t2 => new Template {StatusId = 2});

This is only a workaround, at the end if you need to do different changes for each Template you will need to modify the entity status.