Lambda 表达式中 动态解析OrderbyLinQ语句的实现

添加方法：

        public static IOrderedQueryable<T> OrderBy<T>(this IEnumerable<T> source, string property,string orderType)
        {
            if(orderType.ToLower()=="desc")
                return ApplyOrder<T>(source, property, "OrderByDescending");
            return ApplyOrder<T>(source, property, "OrderBy");
        }
        public static IOrderedQueryable<T> OrderBy<T>(this IEnumerable<T> source, string property)
        {
            return ApplyOrder<T>(source, property, "OrderBy");
        }
        public static IOrderedQueryable<T> OrderByDescending<T>(this IEnumerable<T> source, string property)
        {
            return ApplyOrder<T>(source, property, "OrderByDescending");
        }
        public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string property)
        {
            return ApplyOrder<T>(source, property, "ThenBy");
        }
        public static IOrderedQueryable<T> ThenByDescending<T>(this IOrderedQueryable<T> source, string property)
        {
            return ApplyOrder<T>(source, property, "ThenByDescending");
        }
        static IOrderedQueryable<T> ApplyOrder<T>(IEnumerable<T> source, string property, string methodName)
        {
            string[] props = property.Split('.');
            Type type = typeof(T);
            ParameterExpression arg = Expression.Parameter(type, property);
            Expression expr = arg;
            //foreach (string prop in props)
            //{
            //    // use reflection (not ComponentModel) to mirror LINQ
            //    PropertyInfo pi = type.GetProperty(prop);
            //    expr = Expression.Property(expr, pi);
            //    type = pi.PropertyType;
            //}
            const BindingFlags flag = BindingFlags.Public | BindingFlags.IgnoreCase | BindingFlags.Instance;
            PropertyInfo pi = type.GetProperty(property,flag);
            expr = Expression.Property(expr, pi);
            type = pi.PropertyType;
            //
            Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
            LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);

            object result = typeof(Queryable).GetMethods().Single(
                    method => method.Name == methodName
                            && method.IsGenericMethodDefinition
                            && method.GetGenericArguments().Length == 2
                            && method.GetParameters().Length == 2)
                    .MakeGenericMethod(typeof(T), type)
                    .Invoke(null, new object[] { source, lambda });
            return (IOrderedQueryable<T>)result;
        }

　　调用语句：

var iqlist = _wMSensorTypeRepository.GetAll()
                //查询
                .WhereIf(input.SearchValue != null && !string.IsNullOrEmpty(input.SearchValue),
                    m =>
                        m.SensorTypeCode.Contains(input.SearchValue) || m.SensorTypeName.Contains(input.SearchValue) ||
                        m.Remarks.Contains(input.SearchValue))
                //排序
                .OrderBy(input.SortColName, input.SortType)
                //页码
                .Skip(input.PageSize*(input.PageNumber - 1)).Take(input.PageSize).ToList();
            var list = Mapper.Map<IList<Entities.WMSensorType>, IList<WMSensorTypeDto>>(iqlist).ToList();

　　交互对象：

/// <summary>
    /// 此类定义了分页查询的输入，包含搜索，排序
    /// </summary>
    public class PageInput
    {
        public PageInput()
        {
            PageNumber = 1;
            PageSize = 20;
            SortColName = "";
            SortType = "asc";
            SearchValue = "";
        }
        public int PageNumber { get; set; }
       
        /// <summary>
        /// 每页记录数
        /// </summary>
        public int PageSize { get; set; }
        /// <summary>
        /// 排序列名称
        /// </summary>
        public string SortColName { get; set; }
        /// <summary>
        /// 排序类型 desc asc 
        /// </summary>
        public string SortType { get; set; }
        /// <summary>
        /// 检索字符
        /// </summary>
        public string SearchValue { get; set; }
    }
    /// <summary>
    /// 页面输出结果
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class PageOutput<T> : IOutputDto
    {
        public int PageNumber { get; set; }
        /// <summary>
        /// 总页数
        /// </summary>
        public int TotalPages { get; set; }
        /// <summary>
        /// 每页记录数
        /// </summary>
        public int PageSize { get; set; }

        public List<T> DataItems { get; set; }
    }