EF列表分页查询(单表、多表)，排除参数为空的条件
在日常使用EF框架查询数据库时，有时传入的参数为空,那么我们应该把该条件排除，不应列入组装的sql中，本篇文件以分页查询为例介绍EF框架的单表、多表的多条件查询，参数为空时排除条件。
首先我们要有派生自DBContext类的数据上下文类，这个类代表数据库连接和数据库模型
public class MyDbContext : DbContext
{
public DbSet<人员信息> PersonBasic{ get; set; }
public DbSet<考核信息> Assess{ get; set; }
}
两个示例的实体类型
用于映射到数据库表的实体类型。也就是数据库的表和字段
public class 人员信息
{
public int Id { get; set; }//id
public string Name { get; set; }//姓名
public string Sex{ get; set; }//性别
public string Age{ get; set; }//年龄
public string IdNumber{ get; set; }//身份证号 与B表身份证相同 可关联
public string State{ get; set; }//状态
//...
}
public class 考核信息
{
public int Id { get; set; }
public string Name { get; set; }
public string Sex{ get; set; }
public string Age{ get; set; }
public string IdNumber{ get; set; }//身份证号
[Column(TypeName = "date")]
public DateTime? Time{ get; set; }//考核时间
public string OrganCode{ get; set; }//机构编号
//...
}
入参实体
public class InputDto{
public string SearchText{get;set;}//一个参数可查询多个条件
public string Sex{get;set;}
public string StartTime{get;set;}
public string EndTime{get;set;}
public string OrganCode{get;set;}
public string State{get;set;}
public string Number{get;set;}
public int PageIndex{get;set;}
public int PageIndex{get;set;}
}
结果返回实体
public class OutPutDto
{
public int Id { get; set; }
public string Name { get; set; }
public string Sex{ get; set; }
public string Age{ get; set; }
public string State{ get; set; }
//...
}
使用dbcontext上下文类进行查询
namespace Test
{
public class AppServiceTest
{
private readonly MyDbContext _context;
public AppServiceTest(MyDbContext context)
{
this._context = context;
}
/// ()
.WhereIf(!string.IsNullOrWhiteSpace(input.EndTime), x => x.Time <= DateTime.Parse(input.EndTime))
.WhereIf(!string.IsNullOrWhiteSpace(input.OrganCode), x => organ.Contains(x.OrganCode))
.WhereIf(input.Number > 0, x => db.GroupBy(y => y.IdNumber)
.Where(group => group.Count() > input.Number)
.Select(group => group.Max(y => y.Id))
.Contains(x.Id)).OrderByDescending(a=>a.Id);
//将以上表达式转换为sql为
//select * from 考核信息 where (Name like '王%' or IdNumber like '王%') and Sex='男' and OrganCode in('37','38') and Id in(select max(Id) from 考核信息 group by IdNumber having count(*)>1) Order By Id Desc
//当然如果Number参数为0对应的sql为
//select * from 考核信息 where (Name like '王%' or IdNumber like '王%') and Sex='男' and OrganCode in('37','38') Order By Id Desc
}
else
{
DbSet<考核信息> kh = _context.考核信息;
DbSet<人员信息> basic = _context.人员信息;
// 定义查询 多表 linq查询
query = from a in kh
join b in basic on a.IdNumber equals b.IdNumber
where
(string.IsNullOrWhiteSpace(input.SearchText) || a.Name.StartsWith(input.SearchText) || a.IdNumber.StartsWith(input.SearchText)) &&
(string.IsNullOrWhiteSpace(input.Sex) || a.Sex == input.sex) &&
(string.IsNullOrWhiteSpace(input.StartTime) || a.Time >= DateTime.Parse(input.StartTime)) &&
(string.IsNullOrWhiteSpace(input.EndTime) || a.Time <= DateTime.Parse(input.EndTime)) &&
(string.IsNullOrWhiteSpace(input.State) || b.State == input.State) &&
(input.Number <= 0 || (from x in kh
group x by x.IdNumber into g
where g.Count() > 1
select g.Max(x => x.Id)).Contains(a.Id))
orderby a.Id descending
select a;
//以上linq表达式对应的sql为
//select * from 考核信息 a Inner JOIN 人员信息 b ON a.IdNumber = b.IdNumber where (a.Name like '王%' or a.IdNumber like '王%') and a.Sex='男' and a.OrganCode in('37', '38') and a.Id in(select max(Id) from 考核信息 group by IdNumber having count(*)>1) Order By a.Id Desc
//当然如果number为0时
//select * from 考核信息 a Inner JOIN 人员信息 b ON a.IdNumber = b.IdNumber where (a.Name like '王%' or a.IdNumber like '王%') and a.Sex='男' and a.OrganCode in('37', '38') Order By a.Id Desc
}
int count= query.Count();//统计总行数
// 分页查询数据
var pageIndex = input.PageIndex;
var pageSize = input.PageSize;
var pageData = query.Skip(pageSize * (pageIndex - 1)).Take(pageSize).ToList();
//这里使用了Mapster中间件可以在包控制管理工具中安装 然后using Mapster;
//意思是将pageData映射成OutPutDto
List<OutPutDto> aaa = pageData.Adapt<List<OutPutDto>>();
return new {items=pageData,total=count};
}
end
看完此篇文章后是不是感觉瞬间豁然开朗？