C#中Linq查询条件动态化

由于Linq查询主要是强类型查询，所以很难做到像sql语句一样，在执行前可以动态拼接。

不过通过方法或者集合方式也可以实现一定的动态化。

1.字段的动态拼接：其实就是对一个数据集多次检索。

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List<Custom_Organization> Default = GetDefault(); List<Custom_Organization> COs = Default; #region 搜索 string OrganizationName = TextBoxOrganizationName.Text.Trim(); string ParentID = TextBoxParentID.Text.Trim(); string CountryName = TextBoxCountryName.Text.Trim(); string RegionName = TextBoxRegionName.Text.Trim();   #region 机构名称 if (OrganizationName != "") {     if (CheckBoxOrganizationName.Checked)     {         var result = from o in COs                      where o.OrganizationName.ToLower() == OrganizationName.ToLower()                      select o;         if (result.Count() > 0)         {             COs = result.ToList();         }     }     else     {         var result = from o in COs                      where o.OrganizationName.Contains(OrganizationName)                      select o;         if (result.Count() > 0)         {             COs = result.ToList();         }     } } #endregion   #region 国家,地区 {     var result = from o in COs                  where o.CountryName.Contains(CountryName) && o.RegionName.Contains(RegionName)                  select o;     if (result.Count() > 0)     {         COs = result.ToList();     } } #endregion   #region 机构类型 List<string> list1 = GetCustom_OrganizationTypes(); if (list1.Count > 0) {     var result = from o in COs                  where list1.Contains(o.OrganizationID)                  select o;     if (result.Count() > 0)     {         COs = result.ToList();     } } #endregion   #region 父机构(包括自己) List<string> list2 = GetParentIDs(); if (list2.Count > 0) {     var result = from o in COs                  where list2.Contains(o.ParentID)|| list2.Contains(o.OrganizationID)                  select o;     if (result.Count() > 0)     {         COs = result.ToList();     } } #endregion   #region 排序 string Order = DropDownListOrder.SelectedValue; if (Order == "2") {     var result = from o in COs                  orderby o.Count descending                  select o;     if (result.Count() > 0)     {         COs = result.ToList();     } } #endregion     #endregion

 

 

2.动态的or操作。可以简单的使用list创建搜索集合。

        #region 搜索
        List<string> list = new List<string>();
        list.Add("str1");
        list.Add("str2");
        list.Add("str3");
        var v = from A in Models
                from B in list
                where A.数据.Contains(B)
                select A;
        #endregion

或者

        #region 搜索
        List<string> list = new List<string>();
        list.Add("str1");
        list.Add("str2");
        list.Add("str3");
        var result = from o in Models
                     where
                     list.All(s => o.数据.Contains(s))
        #endregion

 

3.动态的and操作。可以简单的使用list创建搜索集合。

当然不写方法直接循环执行也可以。

        #region 搜索
        List<string> list = new List<string>();
        list.Add("str1");
        list.Add("str2");
        list.Add("str3");

        List<string> Models = new List<string>();
        foreach (string l in list)
        {
            Models = GetSearch(Models, l);
        }
        #endregion

    List<string> GetSearch(List<string> ss, string str)
    {
        var v = from A in ss
                where A == str
                select A;
        List<string> Models = v.ToList();
        return Models;
    }