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DapperExtensions and reflection implement universal search (ASP.NET)

Y2J

May 03, 2017 pm 01:28 PM

这篇文章主要介绍了Asp.net中使用DapperExtensions和反射来实现一个通用搜索功能，非常不错，具有参考解决价值,需要的朋友可以参考下

前言

　　搜索功能是一个很常用的功能，当然这个搜索不是指全文检索，是指网站的后台管理系统或ERP系统列表的搜索功能。常见做法一般就是在搜索栏上加上几个常用字段来搜索。代码可能一般这样实现

StringBuilder sqlStr = new StringBuilder();
if (!string.IsNullOrEmpty(RealName))
{
  sqlStr.Append(" and RealName = @RealName");
}
if (Age != -1)
{
  sqlStr.Append(" and Age = @Age");
}
if (!string.IsNullOrEmpty(StartTime))
{
  sqlStr.Append(" and CreateTime >= @StartTime");
}
if (!string.IsNullOrEmpty(EndTime))
{
  sqlStr.Append(" and CreateTime <= @EndTime");
}
MySqlParameter[] paras = new MySqlParameter[]{
      new MySqlParameter("@Age", Age),
      new MySqlParameter("@RealName", RealName),
      new MySqlParameter("@StartTime", StartTime),
      new MySqlParameter("@EndTime", EndTime)
    };

这段代码如果遇到下面几个需求，又该如何处理？

再加一个查询字段
RealName需要改成模糊查询
Age需要支持范围查询

可能大多数程序猿想法，这是新的需求，那么就直接改代码，简单粗暴。然后在前台加个age范围文本框，后台再加个if判断，realname的=号就直接改成like，就这样轻松搞定了。但需求总是不断变化，如果一张表有50个字段，同时需要支持其中40个字段查询。我想大都数人第一反应：卧槽，神经病！难道就没有一个通用的办法来解决这种搜索的问题？我想说当然有，本文接下来就用DapperExtensions和反射的来解决这个问题，最终于实现的效果如下图：

DapperExtensions介绍

　　DapperExtensions是基于Dapper的一个扩展，主要在Dapper基础上实现了CRUD的操作。它还提供了一个谓词系统，可以实现更多复杂的高级查询功能。还可以通过ClassMapper来定义实体类和表的映射。

通用搜索功能实现

1.首先创建一个account表，然后增加一个Account类

public class Account
  {
    public Account()
    {
      Age = -1;
    }
    /// <summary>
    /// 账户ID
    /// </summary>
    [Mark("账户ID")]
    public int AccountId { get; set; }
    /// <summary>
    /// 姓名
    /// </summary>
    [Mark("姓名")]
    public string RealName { get; set; }
    /// <summary>
    /// 年龄
    /// </summary>
    [Mark("年龄")]
    public int Age { get; set; }
    /// <summary>
    /// 创建时间
    /// </summary>
    [Mark("创建时间")]
    public DateTime CreateTime { get; set; }
  }

2.为了获取字段对应的中文名称，我们增加一个MarkAttribute类。因为有强大的反射功能，我们可以通过反射动态获取每张表实体类的属性和中文名称。

[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
  public class MarkAttribute : Attribute
  {
    public MarkAttribute(string FiledName, string Description = "")
    {
      this.FiledName = FiledName;
      this.Description = Description;
    }
    private string _FiledName;
    public string FiledName
    {
      get { return _FiledName; }
      set { _FiledName = value; }
    }
    private string _Description;
    public string Description
    {
      get { return _Description; }
      set { _Description = value; }
    }
  }

3.通用搜索思路主要是把搜索功能抽象出一个对象，本质上也就列名、操作符、值组成的一个对象集合，这样就可以实现多个搜索条件的组合。我们增加一个Predicate类

public class Predicate
  {
    /// <summary>
    /// 列名
    /// </summary>
    public string ColumnItem { get; set; }
    /// <summary>
    /// 操作符
    /// </summary>
    public string OperatorItem { get; set; }
    /// <summary>
    /// 值
    /// </summary>
    public object Value { get; set; }
  }

4.然后通过反射Account类的属性加载到前台列名的DropDownList，再增加一个操作符的DropDownList

var columnItems = new List<SelectListItem>();
      //通过反射来获取类的属性
      Type t = Assembly.Load("SearchDemo").GetType("SearchDemo.Models.Account");
      foreach (PropertyInfo item in t.GetProperties())
      {
        string filedName = (item.GetCustomAttributes(typeof(MarkAttribute), false)[0] as MarkAttribute).FiledName;
        columnItems.Add(new SelectListItem() { Text = filedName, Value = item.Name });
      }
      ViewBag.columnItems = columnItems;
      var operatorItems = new List<SelectListItem>()
      {
        new SelectListItem() {Text = "等于", Value = "Eq"},
        new SelectListItem() {Text = "大于", Value = "Gt"},
        new SelectListItem() {Text = "大于或等于", Value = "Ge"},
        new SelectListItem() {Text = "小于", Value = "Lt"},
        new SelectListItem() {Text = "小于或等于", Value = "Le"},
        new SelectListItem() {Text = "模糊", Value = "Like"}
      };
      ViewBag.operatorItems = operatorItems;

5.前台界面实现代码

<!DOCTYPE html>
<html>
<head>
  <title>DapperExtensions通用搜索</title>
  <script src="../../scripts/jquery-1.4.4.min.js" type="text/javascript"></script>
  <script type="text/javascript">
    Date.prototype.format = function (format) {
      var o = {
        "M+": this.getMonth() + 1, //month  
        "d+": this.getDate(), //day  
        "h+": this.getHours(), //hour  
        "m+": this.getMinutes(), //minute  
        "s+": this.getSeconds(), //second  
        "q+": Math.floor((this.getMonth() + 3) / 3), //quarter  
        "S": this.getMilliseconds() //millisecond  
      }
      if (/(y+)/.test(format)) {
        format = format.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
      }
      for (var k in o) {
        if (new RegExp("(" + k + ")").test(format)) {
          format = format.replace(RegExp.$1, RegExp.$1.length == 1 ? o[k] : ("00" + o[k]).substr(("" + o[k]).length));
        }
      }
      return format;
    } 
  </script>
  <style type="text/css">
    ul
    {
      list-style: none;
      padding: 0px;
      margin: 0px;
      width: 590px;
      height: 20px;
      line-height: 20px;
      border: 1px solid #99CC00;
      border-top: 0px;
      font-size: 12px;
    }
    ul li
    {
      display: block;
      width: 25%;
      float: left;
      text-indent: 2em;
    }
    .th
    {
      background: #F1FADE;
      font-weight: bold;
      border-top: 1px solid #99CC00;
    }
  </style>
  <script type="text/javascript">
    var predicates = [];
    var index = 0;
    $(document).ready(function () {
      $("#btnAdd").click(function () {
        var columnItem = $("#columnItems option:selected");
        var operatorItem = $("#operatorItems option:selected");
        var value = $("#value").val();
        if(value == ""){
          alert("请输入值");
          return;
        }
        var predicate = { index: index, columnItem: columnItem.val(), operatorItem: operatorItem.val(), value: value };
        predicates.push(predicate);
        var html = "<ul><li>" + columnItem.text() + "</li><li>" + operatorItem.text() + "</li><li>" + value + "</li><li><a href=&#39;javascript:;&#39; onclick=&#39;del(this," + index + ")&#39;>删除</a></li></ul>"
        $("#predicates ul:last").after(html);
        index++;
      })
      $("#btnSearch").click(function () {
        $.ajax({
          type: "POST",
          url: "home/search",
          data: JSON.stringify(predicates),
          contentType: "application/json",
          success: function (data) {
            if (data.Error != null) {
              alert(data.Error);
              return;
            }
            $("#list .th").nextAll().remove();
            var html = "";
            $.each(data, function (index, item) {
              html += "<ul><li>" + item.AccountId + "</li>";
              html += "<li>" + item.RealName + "</li>";
              html += "<li>" + item.Age + "</li>";
              //转换日期
              var dateMilliseconds = parseInt(item.CreateTime.replace(/\D/igm, ""));
              var date = new Date(dateMilliseconds);
              html += "<li>" + date.format("yyyy-MM-dd hh:mm:ss") + "</li></ul>";
            });
            $("#list .th").after(html);
          }
        });
      })
    })
    function del(obj,index) {
      obj.parentNode.parentNode.remove();
      for (var i = 0; i < predicates.length; i++) {
        if (predicates[i].index == index) {
          predicates.splice(i, 1);
        }
      }
    }
  </script>
</head>
<body>
  <p>
    列名：@Html.DropDownList("columnItems")  操作符：@Html.DropDownList("operatorItems")  值：@Html.TextBox("value")  
    <input id="btnAdd" type="button" value="增加" />  <input id="btnSearch" type="button" value="搜索" />
  </p>
  <br />
  <p id="predicates">
    <ul class="th">
      <li>列名</li>
      <li>操作符</li>
      <li>值</li>
      <li>操作</li>
    </ul>
  </p>
  <br />
  <p id="list">
    <ul class="th">
      <li>账户ID</li>
      <li>姓名</li>
      <li>年龄</li>
      <li>创建时间</li>
    </ul>  
  </p>
</body>
</html>

6.最后通过DapperExtensions的谓词和反射实现搜索方法

 [HttpPost]
    public JsonResult Search(List<Predicate> predicates)
    {
      if (predicates == null)
      {
        return Json(new { Error = "请增加搜索条件" });
      }
      using (var connection = SqlHelper.GetConnection())
      {
        var pga = new PredicateGroup { Operator = GroupOperator.And, Predicates = new List<IPredicate>() };
        foreach (var p in predicates)
        {
          var predicate = Predicates.Field<Account>(GetExpression(p), (Operator)Enum.Parse(typeof(Operator), p.OperatorItem), p.Value);
          pga.Predicates.Add(predicate);
        }
        var list = connection.GetList<Account>(pga);
        return Json(list);
      }
    }
    private static Expression<Func<Account, object>> GetExpression(Predicate p)
    {
      ParameterExpression parameter = Expression.Parameter(typeof(Account), "p");
      return Expression.Lambda<Func<Account, object>>(Expression.Convert(Expression.Property(parameter, p.ColumnItem), typeof(object)), parameter);
    }

　　最终，通过简单的几行代码，在基于DapperExtensions的功能基础上，我们最终实现了一个可以支持多个字段、多个条件、多个操作符的通用查询功能。本文也只是抛砖引玉，只是提供一种思路，还有更多细节没有考虑。比如多个条件的组合可以再增加一个逻辑符来连接、多个条件组合嵌套查询、多表查询等等。

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