using System.Linq;
using System.Linq.Expressions;

namespace Znyc.Cloudcar.Admin.Commons.Extend
{
    /// <summary>
    /// </summary>
    public static class ExtQueryable
    {
        /// <summary>
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="ordering"></param>
        /// <returns></returns>
        public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string ordering)
        {
            System.Type type = typeof(T);
            System.Reflection.PropertyInfo property = type.GetProperty(ordering);
            ParameterExpression parameter = Expression.Parameter(type, "p");
            MemberExpression propertyAccess = Expression.MakeMemberAccess(parameter, property);
            LambdaExpression orderByExp = Expression.Lambda(propertyAccess, parameter);
            MethodCallExpression resultExp = Expression.Call(typeof(Queryable), "OrderBy", new[] { type, property.PropertyType },
                source.Expression, Expression.Quote(orderByExp));
            return source.Provider.CreateQuery<T>(resultExp);
        }

        /// <summary>
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="ordering"></param>
        /// <returns></returns>
        public static IQueryable<T> OrderByDescending<T>(this IQueryable<T> source, string ordering)
        {
            System.Type type = typeof(T);
            System.Reflection.PropertyInfo property = type.GetProperty(ordering);
            ParameterExpression parameter = Expression.Parameter(type, "p");
            MemberExpression propertyAccess = Expression.MakeMemberAccess(parameter, property);
            LambdaExpression orderByExp = Expression.Lambda(propertyAccess, parameter);
            MethodCallExpression resultExp = Expression.Call(typeof(Queryable), "OrderByDescending",
                new[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));
            return source.Provider.CreateQuery<T>(resultExp);
        }
    }
}