.net Core学习笔记2 实现列表的条件筛选，排序，分页

打开vs,完善上次"简单粗暴"的项目 

发现上次的实体类的导航属性有点问题，这是更改后的

namespace ProductMvc.Models
{
    public class ProductType
    {
        public int ID { get; set; }
        public string TypeName { get; set; }

        public ICollection<Product> product { get; set; }//一种类型可能有多个商品，所以是集合
    }
}

namespace ProductMvc.Models
{
    public class Product
    {
        public int ID { get; set; }
        public string ProductName { get; set; }

        public DateTime ProductDate { get; set; }

        public decimal Price { get; set; }
        public int TypeID { get; set; }
        public ProductType ProductType { get; set; }
    }
}

为了列表展示方便我创建了一个专门用于展示的类

 public class ProductViewModel
    {
        public int ID { get; set; }
        public string ProductName { get; set; }

        public DateTime ProductDate { get; set; }

        public decimal Price { get; set; }

        public string TypeName { get; set; }
    }

控制器的Index方法也要做相应的修改

  public async Task<IActionResult> Index(string SortOrder, string SearchString,int id=1)
        {
            ViewData["DATE_KEY"] = string.IsNullOrEmpty(SortOrder) ? "DATE_KEY" : "";
            ViewData["TYPE_KEY"] = SortOrder == "TYPE_KEY" ? "TYPE_KEY" : "";
            ViewData["SerachName"] = SearchString;
  //连接查询
var products = from t in _context.ProductType
                          from  p in _context.Product where 
                           t.ID == p.TypeID 
                           select new ProductViewModel { ID=p.ID,Price = p.Price, ProductDate = p.ProductDate, ProductName = p.ProductName, TypeName = t.TypeName }; 
            //按条件查询
            if(SearchString!=""&&SearchString!=null)
            {
                products = products.Where(p=>p.ProductName.Contains(SearchString));
            }
            //排序
            switch(SortOrder)
            {
                case "DATE_KEY":
                    products = products.OrderByDescending(p=>p.ProductDate);
                    break;
                case "TYPE_KEY":
                    products = products.OrderByDescending(p => p.TypeName);//倒序
                    break;
                default:
                    products = products.OrderBy(p => p.ID);
                    break;
            }
            var pageOption = new PagerInBase
            {
                CurrentPage = id,//当前页数
                PageSize = 3,
                Total = await products.CountAsync(),
                RouteUrl = "/Products/Index"
            };

            //分页参数
            ViewBag.PagerOption = pageOption;

            //数据
            return View(await products.Skip((pageOption.CurrentPage - 1) * pageOption.PageSize).Take(pageOption.PageSize).ToListAsync());
        }

函数中的参数SortOrder用于排序，SearchString条件参数，id为分页参数下面是视图中的代码（有阴影的是修改过的地方）:

@model IEnumerable<ProductMvc.Models.ProductViewModel>
@addTagHelper "ProductMvc.Models.PagerTagHelper,ProductMvc"
@{
    ViewData["Title"] = "Index";
}

<h2>商 品 列 表</h2>

<p>
    <a asp-action="Create"><input type="button" value="新 建" class="btn btn-default" /></a>
</p>
<form asp-action="Index" method="get">
    <p>名称：<input  type="text" name="searchString" value="@ViewData["SerachName"]"/>
    <input type="submit" value="搜索"  class="btn btn-default"/>
        </p>
</form>
<table class="table">
    <thead>
        <tr>
                <th>
                    商品名称
                </th>
                <th>                   
                    <a asp-action="Index" asp-route-SortOrder="@ViewData["DATE_KEY"]">生产日期</a>
                </th>
                <th>
                   价格
                </th>
                <th>
                  <a asp-action="Index" asp-route-SortOrder="@ViewData["TYPE_KEY"]">商品类型</a>
                </th>
            <th></th>
        </tr>
    </thead>
    <tbody>
@foreach (var item in Model) {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.ProductName)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.ProductDate)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Price)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.TypeName)
</td>
            <td>
                <a asp-action="Edit" asp-route-id="@item.ID">编辑</a> |
                <a asp-action="Details" asp-route-id="@item.ID">详情</a> |
                <a asp-action="Delete" asp-route-id="@item.ID">删除</a>
            </td>
        </tr>
}
    </tbody>
</table>
<pager pager-option="ViewBag.PagerOption as PagerInBase"></pager>

分页标签是用TagHelper实现的，这个主要是参考 “神牛步行3”  http://www.cnblogs.com/wangrudong003/ 的博客完成的，直接贴代码，添加类PagerInBase

namespace ProductMvc.Models
{
    #region 分页扩展 PagerInBase

    /// <summary>
    /// 分页option属性
    /// </summary>
    public class PagerInBase
    {
        /// <summary>
        /// 当前页 必传
        /// </summary>
        public int CurrentPage { get; set; }
        /// <summary>
        /// 总条数 必传
        /// </summary>
        public int Total { get; set; }

        /// <summary>
        /// 分页记录数（每页条数 默认每页15条）
        /// </summary>
        public int PageSize { get; set; }

        /// <summary>
        /// 路由地址(格式如：/Controller/Action) 默认自动获取
        /// </summary>
        public string RouteUrl { get; set; }

        /// <summary>
        /// 样式 默认 bootstrap样式 1
        /// </summary>
        public int StyleNum { get; set; }
    }

    /// <summary>
    /// 分页标签
    /// </summary>
    public class PagerTagHelper : TagHelper
    {

        public PagerInBase PagerOption { get; set; }


        public override void Process(TagHelperContext context, TagHelperOutput output)
        {

            output.TagName = "div";

            if (PagerOption.PageSize <= 0) { PagerOption.PageSize = 15; }
            if (PagerOption.CurrentPage <= 0) { PagerOption.CurrentPage = 1; }
            if (PagerOption.Total <= 0) { return; }

            //总页数
            var totalPage = PagerOption.Total / PagerOption.PageSize + (PagerOption.Total % PagerOption.PageSize > 0 ? 1 : 0);
            if (totalPage <= 0) { return; }
            //当前路由地址
            if (string.IsNullOrEmpty(PagerOption.RouteUrl))
            {

                //PagerOption.RouteUrl = helper.ViewContext.HttpContext.Request.RawUrl;
                if (!string.IsNullOrEmpty(PagerOption.RouteUrl))
                {

                    var lastIndex = PagerOption.RouteUrl.LastIndexOf("/");
                    PagerOption.RouteUrl = PagerOption.RouteUrl.Substring(0, lastIndex);
                }
            }
            PagerOption.RouteUrl = PagerOption.RouteUrl.TrimEnd('/');

            //构造分页样式
            var sbPage = new StringBuilder(string.Empty);
            switch (PagerOption.StyleNum)
            {
                case 2:
                    {
                        break;
                    }
                default:
                    {
                        #region 默认样式

                        sbPage.Append("<nav>");
                        sbPage.Append(" <ul class=\"pagination\">");
                        sbPage.AppendFormat("  <li><a href=\"{0}/{1}\" aria-label=\"Previous\"><span aria-hidden=\"true\">«</span></a></li>",
                              PagerOption.RouteUrl,
                              PagerOption.CurrentPage - 1 <= 0 ? 1 : PagerOption.CurrentPage - 1);

                        for (int i = 1; i <= totalPage; i++)
                        {

                            sbPage.AppendFormat("  <li {1}><a href=\"{2}/{0}\">{0}</a></li>",
                             i,
                             i == PagerOption.CurrentPage ? "class=\"active\"" : "",
                             PagerOption.RouteUrl);

                        }

                        sbPage.Append("  <li>");
                        sbPage.AppendFormat("   <a href=\"{0}/{1}\" aria-label=\"Next\">",
                             PagerOption.RouteUrl,
                             PagerOption.CurrentPage + 1 > totalPage ? PagerOption.CurrentPage : PagerOption.CurrentPage + 1);
                        sbPage.Append("    <span aria-hidden=\"true\">»</span>");
                        sbPage.Append("   </a>");
                        sbPage.Append("  </li>");
                        sbPage.Append(" </ul>");
                        sbPage.Append("</nav>");
                        #endregion
                    }
                    break;
            }

            output.Content.SetHtmlContent(sbPage.ToString());
        }

    }
    #endregion
}

最后的效果：

好吧我觉得依然的简单粗暴，在后期我会不断的完善的。

新手上路，还望大佬们指正