easyui datagrid remoteSort的实现 Controllers编写动态的Lambda表达式 IQueryable OrderBy扩展

EF 结合easy-ui datagrid 实现页面端排序
EF动态编写排序Lambda表达式

1、前端页面

var mainListHeight = $(window).height() - 20;
       $(document).ready(function () {
           $("#AppLogGrid").datagrid({
               "title": "应用程序日志记录",
               "iconCls": "icon-blank",
               "width": "100%",
               "height": mainListHeight,
               "nowrap": false,
               "striped": true,
               "pagination": true,
               "rownumbers": true,
               "remoteSort": true,
               "pageList": [50, 100, 200, 500, 1000],
               "frozenColumns": [[
                { "field": "ck", checkbox: true }
            ]],
               "toolbar": "#tb",
               "columns": [[
               { "field": "nId", "title": "序号", "width": 60, "align": "right", "sortable": true },
               { "field": "dtDate", "title": "日志记录时间", "width": 120, "align": "center", "sortable": true },
               { "field": "sLevel", "title": "日志等级", "width": 80, "align": "center", "sortable": true },
               { "field": "sLogger", "title": "Logger类", "width": 80, "align": "left" },
               { "field": "sMessage", "title": "日志内容", "width": 660, "align": "left" }
           ]]
           })
           //初始化
           loadGrid();
       });
       //刷新表格
       function loadGrid() {
           var p = {
               "url": "/CommonBiz/GetAppLogList",
               "data": {
                   "Parameter": {
                       "LogLevel": $("#logLevel").val()
                   }
               }
           }
           $("#AppLogGrid").datagrid({ "url": p.url, "queryParams": { "Parameter": $.toJSON(p.data)} });
       }

设置了“dtDate”和“sLevel”　两个字段允许( "remoteSort": true)在页面排序。

2、后端Controller代码

/// <summary>
        /// 获取某类型日志记录
        /// </summary>
        /// <returns></returns>
        public JsonResult GetAppLogList()
        {
            using (Reserve_DbEntities db = new Reserve_DbEntities())
            {
                var list = new List<AppSystemLog>();
                string queryParams = Request.Form["Parameter"];
                int pageRowNum = int.Parse(Request.Form["rows"]);
                int pageIndex = int.Parse(Request.Form["page"]);
                string sortField = Request.Form["sort"] as string;
                string order = Request.Form["order"] as string;
                if (!string.IsNullOrEmpty(queryParams))
                {
                    var resultJson = JObject.Parse(queryParams);
                    string level = resultJson["Parameter"]["LogLevel"].Value<string>();
                    if (string.IsNullOrEmpty(sortField))
                    {
                        if (level.Equals("ALL"))
                            list = db.AppSystemLog.OrderByDescending(l => l.nId).ToList();
                        else list = db.AppSystemLog.Where(l => l.sLevel == level).OrderByDescending(o => o.dtDate).ToList();
                    }
                    else
                    {
                        if (level.Equals("ALL"))
                            list = db.AppSystemLog.OrderBy<AppSystemLog>(sortField, order.Equals("asc") ? true : false).ToList();
                        else list = db.AppSystemLog.Where(l => l.sLevel == level).OrderBy<AppSystemLog>(sortField, order.Equals("asc") ? true : false).ToList();
                    }
                }
                var resultRows = list.Skip((pageIndex - 1) * pageRowNum).Take(pageRowNum).ToList();
                var jsonResult = new { total = list.Count, rows = resultRows };
                return Json(jsonResult, JsonRequestBehavior.AllowGet);
            }
        }

这里的技巧是需要扩展IQueryable,因为一般写法是 list.OrderBy(o=>o.XXXX字段“显示的写法”)。而页面post过来的字段名称是会变的，这样后端必须实现动态编写Lambda表达式，一翻搜索发现扩展的方法：

/// <summary>
    /// IQueryable扩展
    /// </summary>
    public static class QueryableExter
    {
        public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string propertyName, bool ascending) where T : class
        {
            Type type = typeof(T);
            PropertyInfo property = type.GetProperty(propertyName);
            if (property == null)
                throw new ArgumentException("propertyName", "Not Exist");
            ParameterExpression param = Expression.Parameter(type, "p");
            Expression propertyAccessExpression = Expression.MakeMemberAccess(param, property);
            LambdaExpression orderByExpression = Expression.Lambda(propertyAccessExpression, param);
            string methodName = ascending ? "OrderBy" : "OrderByDescending";
            MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName, new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExpression));
 
            return source.Provider.CreateQuery<T>(resultExp);
        }
    }