C＃Linq对模型使用变量

Question

Trying to write a piece of code that is dynamic in that it can accept any number of possible model definitions.

Current hard code is:

var items = _context.Events.ToList();

foreach (var item in items)
{
     (...)
}

What I would like to do is to make the _context.Events.ToList(); be more like _context.{variable that holds model name}.ToList();

Something like:

var modelName = "Table1"
var items = _context.modelName.ToList();

foreach (var item in items)
{
     (...)
}

I thought about declaring items as a generic variable, that way it was available to the entire method even if set inside an if or switch, but no idea on what to declare it as.

Is something like this possible?

Answer 1

Try this :

var table = (ITable)context.GetType()
                           .GetProperty(modelName)
                           .GetValue(context, null);

I hope be helpful :)

Answer 2

Entity Framework has a generic Set<TEntity> accessor, but the type must be known at compile-time:

var foo = _context.Set<Foo>();

If you have the type as a string variable, though, your options are extremely limited. You can technically use reflection to get at the right DbSet , but you're going to lose the generic IQueryable<TEntity> interface, and you'll be stuck with the much more limited IQueryable interface, and by "much more limited", I mean you basically can't do anything but materialize the set.

If you want to type it via a string variable, but still have at least some querying ability, you'll need to employ a base class that's shared between all the entity types you'd want to use in this way. For example, if you have different "event" types, and you can make them all inherit from Event , then you could do something like:

MethodInfo method = typeof(Queryable).GetMethod("OfType");
MethodInfo generic = method.MakeGenericMethod(new Type[] { eventType });
var set = (IQueryable<Event>)generic.Invoke(null, new object[] { _context.Events });

If your eventType was "Film", for example, that would effectively give you the same queryset as something like _context.Set<Film>() (where Film would be a derived class of Event ). You could then utilize your normal LINQ query functionality like Where , Select , etc. on set .