linq 动态排序

/// <summary>
       /// 排序
       /// </summary>
       /// <typeparam name="T"></typeparam>
       /// <param name="source"></param>
       /// <param name="sortExpression"></param>
       /// <param name="sortDirection"></param>
       /// <returns></returns>
        public static IQueryable<T> DataSorting<T>(IQueryable<T> source, string sortExpression, string sortDirection)
        {
            string sortingDir = string.Empty;
            if (sortDirection.ToUpper().Trim() == "ASC")
                sortingDir = "OrderBy";
            else if (sortDirection.ToUpper().Trim() == "DESC")
                sortingDir = "OrderByDescending";
            ParameterExpression param = Expression.Parameter(typeof(T), sortExpression);
            PropertyInfo pi = typeof(T).GetProperty(sortExpression);
            Type[] types = new Type[];
            types[] = typeof(T);
            types[] = pi.PropertyType;
            Expression expr = Expression.Call(typeof(Queryable), sortingDir, types, source.Expression, Expression.Lambda(Expression.Property(param, sortExpression), param));
            IQueryable<T> query = source.AsQueryable().Provider.CreateQuery<T>(expr);
            return query;
        }