NFine完善列表页多字段排序

问题描述：之前尝试列表页定义两个排序字段你，但是总按照最后面的字段来，并没有按照多字段排序。。。

解决方案：昨晚深入琢磨了半天，找到了排序的相关代码

        public async Task<List<T>> FindList(Expression<Func<T, bool>> predicate, Pagination pagination)
        {
            bool isAsc = pagination.sord.ToLower() == "asc" ? true : false;
            string[] _order = pagination.sidx.Split(',');
            MethodCallExpression resultExp = null;
            var tempData = Repository.Find(predicate);
            foreach (string item in _order)
            {
                string _orderPart = item;
                _orderPart = Regex.Replace(_orderPart, @"\s+", " ");
                string[] _orderArry = _orderPart.Split(' ');
                string _orderField = _orderArry[0];
                bool sort = isAsc;
                if (_orderArry.Length == 2)
                {
                    isAsc = _orderArry[1].ToUpper() == "ASC" ? true : false;
                }
                var parameter = Expression.Parameter(typeof(T), "t");
                var property = typeof(T).GetProperty(_orderField);
                var propertyAccess = Expression.MakeMemberAccess(parameter, property);
                var orderByExp = Expression.Lambda(propertyAccess, parameter);
                resultExp = Expression.Call(typeof(Queryable), isAsc ? "OrderBy" : "OrderByDescending", new Type[] { typeof(T), property.PropertyType }, tempData.Expression, Expression.Quote(orderByExp));
            }
            tempData = tempData.Provider.CreateQuery<T>(resultExp);
            pagination.records = tempData.Count();
            tempData = tempData.Skip<T>(pagination.rows * (pagination.page - 1)).Take<T>(pagination.rows).AsQueryable();
            return await tempData.ToListAsync();
        }

可以看到是允许传入多排序参数的，而且代码里也做了相关处理，结合起来linq中两个orderby肯定会执行最后一次，这个地方是欠缺使用thenby，所以整改起来

        public async Task<List<T>> FindList(Expression<Func<T, bool>> predicate, Pagination pagination)
        {
            bool isAsc = pagination.sord.ToLower() == "asc" ? true : false;
            string[] _order = pagination.sidx.Split(',');
            MethodCallExpression resultExp = null;
            var tempData = Repository.Find(predicate);
            var tempCurrent = 0;
            foreach (string item in _order)
            {
                string _orderPart = item;
                _orderPart = Regex.Replace(_orderPart, @"\s+", " ");
                string[] _orderArry = _orderPart.Split(' ');
                string _orderField = _orderArry[0];
                bool sort = isAsc;
                if (_orderArry.Length == 2)
                {
                    isAsc = _orderArry[1].ToUpper() == "ASC" ? true : false;
                }
                var parameter = Expression.Parameter(typeof(T), "t");
                var property = typeof(T).GetProperty(_orderField);
                var propertyAccess = Expression.MakeMemberAccess(parameter, property);
                var orderByExp = Expression.Lambda(propertyAccess, parameter);
                if (tempCurrent == 0)
                {
                    resultExp = Expression.Call(typeof(Queryable), isAsc ? "OrderBy" : "OrderByDescending", new Type[] { typeof(T), property.PropertyType }, tempData.Expression, Expression.Quote(orderByExp));
                }
                else
                {
                    resultExp = Expression.Call(typeof(Queryable), isAsc ? "ThenBy" : "ThenByDescending", new Type[] { typeof(T), property.PropertyType }, tempData.Expression, Expression.Quote(orderByExp));
                }
                tempData = tempData.Provider.CreateQuery<T>(resultExp);
                tempCurrent++;
            }
            pagination.records = tempData.Count();
            tempData = tempData.Skip<T>(pagination.rows * (pagination.page - 1)).Take<T>(pagination.rows).AsQueryable();
            return await tempData.ToListAsync();
        }

黄色标识的代码是重点，如果放到循环外面会报错，错误代码如下：

No generic method 'ThenByDescending' on type 'System.Linq.Queryable' is comp...

意思大概是没有执行orderby而直接执行thenby的错误，所以把这句放到了里面来执行，虽然整体代码也看不懂，但逻辑上也确实应该放到里面，至此问题解决。。。