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题前:,Select new{"需要的字段列.."}好处,减少不必要数据的查询,尤其是分布式的时候,网络再不好的情况下,而不必要的数据又很多,Select new{"需要的字段列.."}好处明显

如题,Linq多表链接分页,Select new{"需要的字段列.."},配合杨涛Mvcpager,前台遍历展示自定义字段

(1)  我的例子是,(Tb_Mnager)管理员表与(Tb_Role)角色表联查,返回两个表部分字段的组合

如下控制器代码:

public ActionResult List(int? pager)  
{  
    pager = pager ?? 1;  
    int pageSize =20;  
    MyMvcCmsEntities db = new MyMvcCmsEntities();  
    //多表链接查询,Select new{}返回需要的字段  
    //注意此处,rs实际会是一个List<Object>对象,如何在视图中遍历???答:反射  
    var rs = (from m in db.Tb_Manager  
             join r in db.Tb_Role on m.roleId equals r.id orderby m.sequeNum descending  
             select new  
             {  
                 m.id,  
                 //自定义的状态,sql语句会转化为case..when..then  
                 status = m.isDisable == 1 ? "<font color='red'>禁用</font>" : "<font color='green'>正常</font>",  
                 m.loginName,  
                 m.sequeNum,  
                 m.date,  
                 //角色表中的角色名字  
                 r.roleName  
             });  
    //查询总数----sql事件探查器可知:此处会查询一次数据库  
    ViewBag.allCount = rs.Count();  
    //本语句会自动生成select top....,并把结果List<Object>返回----此处会查询二次数据库  
    ViewBag.list = rs.ToPagedList((int)pager, pageSize);  
    return View();  
}  

  好了,结果返回了,那么前台如何遍历遍历List<Object>的值呢?

答案:反射 详情 C#反射的简单应用

此处,我用反射原理,写了一个帮助类:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Reflection;  
using System.Text;  
using System.Threading.Tasks;  
  
namespace Mvc.Util  
{  
   public class Reflection  
   {  
  
       /// <summary>  
       /// 获取指定属性的值(不区分大小写)  
       /// </summary>  
       /// <param name="PropertyName">属性名称</param>  
       /// <param name="o">目标对象</param>  
       /// <returns></returns>  
       public static Object GetPropertyValueByName(string PropertyName, Object o)  
       {  
           if (o == null)  
           {  
               o = new { };  
           }  
           //创建一个返回对象  
           Object returnObject = new Object();  
           PropertyInfo[] p1 = o.GetType().GetProperties();  
           foreach (PropertyInfo pi in p1)  
           {  
               if (pi.Name.ToLower() == PropertyName.ToLower())  
               {  
                   returnObject = pi.GetValue(o);  
               }  
           }  
           return returnObject;  
       }  
  
   }  
}  

@{int index = 0;}  
@foreach (Object t in ViewBag.list)  
{  
    index++;  
    <tr>  
        <td align="center"><span class="checkall" style="vertical-align:middle;"><input class="list-box" value="@Reflection.GetPropertyValueByName("id", t).ToString()" type="checkbox" /></span></td>  
        <td>@index</td>  
        <td>@Reflection.GetPropertyValueByName("loginName", t).ToString()</td>  
        <td>  
            @Reflection.GetPropertyValueByName("roleName", t).ToString()  
        </td>  
        <td>@Reflection.GetPropertyValueByName("date", t).ToString()</td>  
        <td>  
            @Html.Raw(Reflection.GetPropertyValueByName("status", t).ToString())  
        </td>  
        <td>  
            <input type="text" value="@Reflection.GetPropertyValueByName("sequeNum", t).ToString()" class="sort" />  
        </td>  
        <td align="center"><a href='@Url.Action("edit", "manager", new { area="cms",id=Reflection.GetPropertyValueByName("id", t).ToString()})'>修改</a></td>  
    </tr>  
}  

@Html.Pager((IPagedList)ViewBag.list, new PagerOptions { PageIndexParameterName = "pager", ShowPageIndexBox = false, PageIndexBoxType = PageIndexBoxType.TextBox, ShowGoButton = false, FirstPageText = "首页", LastPageText = "尾页", ShowFirstLast = true, CurrentPagerItemWrapperFormatString = "<span class=\"current\">{0}</span>", CssClass = "default" }, new { @style = "width:100%;float=left;" })