目录
- [LINQ2Dapper]最完整Dapper To Linq框架(一)---基础查询
- [LINQ2Dapper]最完整Dapper To Linq框架(二)---动态化查询
- [LINQ2Dapper]最完整Dapper To Linq框架(三)---实体类关系映射
- [LINQ2Dapper]最完整Dapper To Linq框架(四)---Linq和SQL并行使用
- [LINQ2Dapper]最完整Dapper To Linq框架(五)---查看Linq实际执行的SQL
- [LINQ2Dapper]最完整Dapper To Linq框架(六)---多表联合与匿名类型返回
- [LINQ2Dapper]最完整Dapper To Linq框架(七)---仓储模式
- [LINQ2Dapper]最完整Dapper To Linq框架(八)---导航属性
1.多表联合查询
默认情况下Where,Get,ToList,PageList等函数只支持单表操作，
如
var comment = conn.QuerySet<Comment>()
.Where(x => x.Id.NotIn(new int[] { 1, 2, 3 })
&& x.SubTime.AddMinutes(50) < DateTime.Now.AddDays(-1)
&& x.Type.IsNotNull())
.ToList();
3.1.2后支持双表和三表同时映射操作，需要通过From函数指定映射表，
如
var comment = conn.QuerySet<Comment>()
.From<Comment, News, ResourceMapping>()
.Where((a, b, c) => a.Id == 1
&& b.Headlines.IsNotNull()
&& c.RSize > 100);
也可以通过GetQuerySet()返回基础的QuerySet对象
var comment = conn.QuerySet<Comment>()
.From<Comment, News, ResourceMapping>()
.Where((a, b, c) => a.Id == 1
&& b.Headlines.IsNotNull()
&& c.RSize > 100)
.GetQuerySet()
.ToList();
以上是三表联合查询，如果有更多表联合需求可以通过自己扩展实现，
如
/// <summary>
/// 定义一个四表联合扩展类
/// </summary>
/// <typeparam name="T">对应QuerySet的泛型</typeparam>
/// <typeparam name="T1">扩展泛型1</typeparam>
/// <typeparam name="T2">扩展泛型2</typeparam>
/// <typeparam name="T3">扩展泛型3</typeparam>
/// <typeparam name="T4">扩展泛型4</typeparam>
public class testFrom<T, T1, T2, T3,T4> : ISelect<T>
{
public testFrom(QuerySet<T> querySet) : base(querySet)
{
}
//定义了一个Where
public testFrom<T, T1, T2, T3,T4> Where(Expression<Func<T1, T2, T3,T4, bool>> select)
{
base.Where(select);
return this;
}
//定义了一个ToList
public IEnumerable<TReturn> ToList<TReturn>(Expression<Func<T1, T2, T3,T4, TReturn>> select)
{
return base.ToList<TReturn>(select);
}
}
然后使用扩展类
//首先声明一个QuerySet
var querySet = conn.QuerySet<Comment>();
/*把定义的querySet实例带入到扩展类中
（注意：第一个T类型必须对应querySet的泛型，如Comment）*/
var list = new testFrom<Comment, Comment, News, ResourceMapping, LikeRecord>(querySet)
.Where((a, b, c, d) => a.Id == 1
&& b.NewsLabel.Contains("t"))
.GetQuerySet()
.ToList();
以此类推，可以任意扩展联表的数量
以下是支持的函数
public class ISelect<T>
{
public ISelect(QuerySet<T> querySet);
public TReturn Get<TReturn>(LambdaExpression exp);
public QuerySet<T> GetQuerySet();
public ISelect<T> OrderBy<TProperty>(Expression<Func<TProperty, object>> field);
public ISelect<T> OrderByDescing<TProperty>(Expression<Func<TProperty, object>> field);
public PageList<TReturn> PageList<TReturn>(int pageIndex, int pageSize, LambdaExpression exp);
public IEnumerable<TReturn> ToList<TReturn>(LambdaExpression exp);
public QuerySet<T> Where(LambdaExpression exp);
}
2.结果返回匿名类型
3.12版本后支持返回匿名类型，
如
var comment = conn.QuerySet<Comment>()
.Where(x => x.Content == "test1" && x.Content.Contains("t"))
.Get(x => new
{
Id = 123,
ArticleId = x.ArticleId
});
一些复杂的字段返回可以通过sql实现，
例如
var comment = conn.QuerySet<Comment>()
.Join<Comment, News>((a, b) => a.ArticleId == b.Id)
.Where(x => x.Content == "test1" && x.Content.Contains("t"))
.Where<Comment, News>((a, b) => a.SubTime < DateTime.Now.AddDays(-5) && a.Id > a.Id % 1)
.Get(x => new
{
count = Convert.ToInt32("(select count(1) from Comment_4)"),
aaa = "6666",
});
并且也支持联合查询的返回
var comment = conn.QuerySet<Comment>()
.Join<Comment, News>((a, b) => a.ArticleId == b.Id)
.Join<Comment, ResourceMapping>((a, b) => a.Id == b.FKId)
.Where(x => x.Content == "test")
.From<Comment, News, ResourceMapping>()
.OrderBy<News>(x => x.Id)
.Where((a, b, c) => a.ArticleId == b.Id)
.PageList(1, 10, (a, b, c) => new
{
id = a.Id,
name = b.NewsLabel,
resource = c.RPath,
rownum = Convert.ToInt32("ROW_NUMBER() OVER(ORDER BY Comment.Id)"),
NewsLable = "News.NewsLabel"
});
还支持比较复杂的子查询
子查询支持的函数有 Count() Sum<T>(字段)
例如
var comment1 = conn.QuerySet<Comment>()
.Join<Comment, News>((a, b) => a.ArticleId == b.Id)
.Where(x => x.Id.Between(80, 100)
&& x.SubTime.AddDays(-10) < DateTime.Now && x.Id > 10)
.From<Comment, News>()
.Get((a, b) => new
{
//(不查询数据库的方法可以任意使用)
test = new List<int>() { 3, 3, 1 }.FirstOrDefault(y => y == 1),
aaa = "6666" + "777",
Content = a.Content + "'test'" + b.Headlines + a.IdentityId,
//此字段会拼接成子查询，不用担心循环查询造成的性能问题
bbb = new QuerySet<Comment>(conn, new MySqlProvider())
.Where(y => y.ArticleId == b.Id && y.Content.Contains("test")).Sum<Comment>(x => x.Id),
ccc = a.IdentityId,
ddd = Convert.ToInt32("(select count(1) from Comment)")
});
完整Demo可以去Github上下载：
https://github.com/a935368322/Kogel.Dapper.Test
如有问题也可以加QQ群讨论：
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