Dynamic table name in linq

I'm trying to execute some LINQ commands using a dynamic table name. For example, instead of

var o = (from x in context.users select x);

I want to use something like

var o = (from x in getTableObjectByName("users", context) select x);

More or less. Here's the code I have so far, which both compiles and runs:

using (MySiteEntities ipe2 = new MySiteEntities()) {
    var propinfo1 = Type.GetType("MySiteNamespace.MySiteEntities").GetProperty("users");
    var propval1 = propinfo1.GetValue(ipe2, null);
}

That runs, but always returns zero records. The users table most definitely contains records, and in any case when I call it directly using the first method above I get all of the records as expected. How can I modify my code to actually pull down records, rather than just an empty collection?

Edit: I've also tried this:

using (MySiteEntities ipe = new MySiteEntities())
{
    var prop = Type.GetType("MySiteNamespace.MySiteEntities").GetProperty("users");
    Type dbsetType = typeof(DbSet<>);
    dbsetType = dbsetType.MakeGenericType(Type.GetType("MySiteNamespace.user"));

    Type t = dbsetType.GetType();
    var val = prop.GetValue(ipe, null);
}

In this case, the code not only runs, but actually returns the results as expected. However, val is an Object. I need to cast it to the type DbSet<user>, which would be easy enough, except that the parameter user is only known at runtime....the cast needs to be dynamic as well. I've tried using Convert.ChangeType(val, t);, but that throws an InvalidCastException (Object must implement IConvertible).

How can I convert the val variable to an actually usable object?

No idea if this is relevant, but this is on EntityFramework 4.