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Dynamic LINQ Expression for sorting navigation property

public class UniversityMaster

    {

        [Key]

        public string UniversityId { get; set; }

        public string UniversityName { get; set; }

 

    }

 

    public class ProgramMaster

    {

        [Key]

        public string ProgramId { get; set; }

        public string ProgramName { get; set; }

        public string UniversityId { get; set; }

 

        public virtual UniversityMaster University { get; set; } // navigation property

 

    }

       

public virtual IQueryable< ProgramMaster > GetQueryableSort(string sortField="", string sortDirection="")

        {

            IQueryable<ProgramMaster> query = _dbSet;

 

            ParameterExpression pe = Expression.Parameter(typeof(ProgramMaster), string.Empty);

            MemberExpression property = Expression.PropertyOrField(pe, sortField); //get a exception here if the sort field is of navigation property (University.UniversityName)

 

            LambdaExpression lambda = Expression.Lambda(property, pe);

 

 

 

            if (sortDirection == "ASC")

                orderbydir = "OrderBy";

            else

                orderbydir = "OrderByDescending";

 

            MethodCallExpression call = Expression.Call(typeof(Queryable),

                    orderbydir, new Type[] { typeof(TEntity), property.Type }, query.Expression, Expression.Quote(lambda));

 

            var returnquery = (IOrderedQueryable<ProgramMaster>)query.Provider.CreateQuery< ProgramMaster >(call);

 

            return returnquery;

        }