CostCalculationItem/IRaCIS.Core.Application/_ExpressionExtend/QueryableExtension.cs

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

namespace IRaCIS.Application.ExpressionExtend
{
    public static class QueryableExtension
    {
        public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> query, string propertyName)
        {
            Type type = typeof(T);

            PropertyInfo property = type.GetProperty(propertyName);
            if (property == null)
                throw new ArgumentException(propertyName, "Not Exist");

            return OrderBy<T>(query, propertyName, false);
        }

        public static IOrderedQueryable<T> OrderByDescending<T>(this IQueryable<T> query, string propertyName)
        {
            Type type = typeof(T);

            PropertyInfo property = type.GetProperty(propertyName);
            if (property == null)
                throw new ArgumentException(propertyName, "Not Exist");

            return OrderBy<T>(query, propertyName, true);
        }

        static IOrderedQueryable<T> OrderBy<T>(IQueryable<T> query, string propertyName, bool isDesc)
        {
            string methodName = (isDesc) ? "OrderByDescendingInternal" : "OrderByInternal";

            var memberProp = typeof(T).GetProperty(propertyName);

            var method = typeof(QueryableExtension).GetMethod(methodName)

                .MakeGenericMethod(typeof(T), memberProp.PropertyType);

            return (IOrderedQueryable<T>)method.Invoke(null, new object[] { query, memberProp });
        }

        public static IOrderedQueryable<T> OrderByInternal<T, TProp>(IQueryable<T> query, System.Reflection.PropertyInfo memberProperty)
        {
            return query.OrderBy(_GetLamba<T, TProp>(memberProperty));
        }

        public static IOrderedQueryable<T> OrderByDescendingInternal<T, TProp>(IQueryable<T> query, System.Reflection.PropertyInfo memberProperty)
        {
            return query.OrderByDescending(_GetLamba<T, TProp>(memberProperty));
        }

        static Expression<Func<T, TProp>> _GetLamba<T, TProp>(System.Reflection.PropertyInfo memberProperty)
        {
            if (memberProperty.PropertyType != typeof(TProp)) throw new Exception();

            var thisArg = Expression.Parameter(typeof(T));
            var lamba = Expression.Lambda<Func<T, TProp>>(Expression.Property(thisArg, memberProperty), thisArg);
            return lamba;
        }

    }
}