Q:

Instance Property is not defined for type 'System.Int64'

I am using a Repository Pattern to access data using Entity Framework. I have implemented everything correctly (I think) using an onion architecture, but when I run tests I get the error :
Instance Property 'IDDocument' is not defined for type 'System.Int64'

(roughly translated from french)
The method I test is the following:
public T Get(long id)
{
    ObjectContext objContext = ((IObjectContextAdapter)context).ObjectContext;
    ObjectSet<T> set = objContext.CreateObjectSet<T>();
    IEnumerable<string> keyNames = set.EntitySet.ElementType
                                                .KeyMembers
                                                .Select(k => k.Name);
    if (keyNames.Count() > 1)
        return null;//Que faire quand il y a plusieurs clés?
    else
    {
        string idName = keyNames.ElementAt(0); // For Document would be IDDocument
        var parameter = Expression.Parameter(id.GetType());
        var property = Expression.Property(parameter, idName);
        var idValue = Expression.Constant(id, id.GetType());
        var equal = Expression.Equal(property, idValue);
        var predicate = Expression.Lambda<Func<T, bool>>(equal, parameter);
        return entities.SingleOrDefault(predicate);
    }
}

My tables have different ID names for reasons I won't explain, but this is why I used Expression builder to add parameters and then use a predicate to retrieve my result. You can see this method in this post: Does a Generic Repository need a Base Entity class to be applied everywhere?
IDDocument is declared in the following way in my EF entities' POCO:
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long IDDocument { get; set; }

And when I call it in my test:
[TestMethod]
public void IdExistsGetTest()
{
    long valueToCheck = 1L;
    repo = new Repository<Web_Documents>(context);
    var test = repo.Get(valueToCheck);
    test.Should().BeOfType(typeof(Web_Documents));
}

context defines my dbcontext (instantiated before).
Now when I run the tests, I always get the ArgumentException stated above, any idea what I am missing? I think the problem resides in the Get(long id) method, because if I change the code without the Expression, it works fine (but not like i want it to!). Thanks

A:

I think:
var parameter = Expression.Parameter(id.GetType());

Should be:
var parameter = Expression.Parameter(typeof(T));

