Dynamically paging EF Core results - .net-core

Question

I have a UI grid which permits sorting by column :
Id
Organisation Name
Organisation type
Departments
1
first
some type
def
2
second
another type
abc, def
2
third
some type
xyz
See the entities below:
public class Organisation
{
public int Code { get; set; }
public string Type { get; set; }
public string Name { get; set; }
public List<Department> Departments { get; set; }
}
public class Department
{
public int Code { get; set; }
public string Name { get; set; }
}
I want to be able to sort the table values by Departments which is a comma separated values that comes from Organization.Departments.Select(p=> p.Name);
I would like to make the sorting as an IQueryable and avoid bringing all the data in memory because After sorting I will apply the pagination and I don't want to bring all the DB records in memory.
I'm using the following extension method for sorting, but it is not working for nested collections:
public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string sortProperty, ListSortDirection sortOrder)
{
var type = typeof(T);
var property = type.GetProperty(sortProperty, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
if (property == null)
throw new OperationFailedException($"Sorting by {sortProperty}");
var parameter = Expression.Parameter(type, "p");
var propertyAccess = Expression.MakeMemberAccess(parameter, property);
var orderByExp = Expression.Lambda(propertyAccess, parameter);
var typeArguments = new Type[] { type, property.PropertyType };
var methodName = sortOrder == ListSortDirection.Ascending ? "OrderBy" : "OrderByDescending";
var resultExp = Expression.Call(typeof(Queryable), methodName, typeArguments, source.Expression, Expression.Quote(orderByExp));
return source.Provider.CreateQuery<T>(resultExp);
}
This method works fine for properties that are at object level.
IQueryable I'm using later for sorting looks something like this:
var iQueryableToBeSorted = _dbContext.Organization.Include(p=>p.Departments).AsQueryable();