Expression of type 'System.Int64' cannot be used for return type 'System.Object'

I am trying to create an expression of the following form:

e => e.CreationDate;

CreationDate is of type long, however I want the expression to return an object instead.

I want to use object as a return type because the expression is built dynamically at runtime based on a query paramater. The query parameter specifies the property to access in the expression, such as:

> entities?order=creationDate
> entities?order=score

As you can see, I can order by different properties with different types, so a return type object would allow me to build the expression as generic as possible.

The problem is that when I try to create the expression:

ParameterExpression entityParameter = Expression.Parameter(typeof(Entity), "e");
Expression propertyAccess = Expression.Property(entityParameter, property);
Expression<Func<Entity, object>> result = Expression.Lambda<Func<Entity, object>>(propertyAccess, entityParameter);

I get the following exception:

Expression of type 'System.Int64' cannot be used for return type 'System.Object'

It is strange, because as far as I know, all types extend from object (It seems polymorphism is not yet supported by expression trees).

Nevertheless, I searched on the web and stumbled with this similar question:

Expression of type 'System.Int32' cannot be used for return type 'System.Object'

Following Jon Skeet's answer, I modified my last line to:

Expression<Func<Entity, object>> result = Expression.Lambda<Func<Entity, object>>(Expression.Convert(propertyAccess, typeof(object)), entityParameter);

This works fine, but it doesn't generate the expression I want. Instead, it generates something like this:

e => Convert(e.CreationDate)

I cannot use this solution, because later in the program an exception is thrown if the expression body is not a MemberExpression (i.e., a member access operation)

I kept searching on the Internet for a satisfying answer, but couldn't find any.

How can I achieve e => e.CreationDate where return type is object?