集合中的 Dapper Multipmapping 集合
Dapper Multipmapping collection within collections
在 Dapper 中,映射和对象包含列表并且每个列表项都有自己的列表的最佳方式是什么?
class Object1 {
int Object1Id;
List<Object2> object2s;
}
class Object2 {
int Object2Id;
List<Object3> object3s;
}
class Object3 {
int Object3Id;
}
这是我想使用的SQL
SELECT *
FROM [Object1] o1
left join [Object2] o2 on o1.Object1Id = o2.Object1Id
left join [Object3] o3 on o2.Object2Id = o3.Object2Id
使用左连接,因为 Object1 可能没有 Object2,而 Object2 可能没有任何 Object3
我考虑过使用
connection.Query<Object1, Object2, Object3, Object1>
但是在字典中跟踪字典以将它们添加到列表中似乎需要很多行代码。
使用 QueryMultiple 会更好吗?
你完全正确:这种父子处理不是 dapper 现在处理得很好的场景。如果它这样做了就好了,但它根本不是做某事的首要任务。
您可以选择两种不雅的解决方案。我个人认为 QueryMultiple
方法可能更简洁。
如果您使用 SQL Server 2016 或更高版本,我会选择 JSON。您可以 return 将数据作为 JSON 文档,如下所示:
USE tempdb
GO
DROP TABLE IF EXISTS dbo.[Object1]
DROP TABLE IF EXISTS dbo.[Object2]
DROP TABLE IF EXISTS dbo.[Object3]
GO
CREATE TABLE dbo.[Object1] ([Object1Id] INT PRIMARY KEY, [Value1] NVARCHAR(100));
CREATE TABLE dbo.[Object2] ([Object2Id] INT PRIMARY KEY, [Object1Id] INT, [Value2] NVARCHAR(100));
CREATE TABLE dbo.[Object3] ([Object3Id] INT PRIMARY KEY, [Object2Id] INT, [Value3] NVARCHAR(100));
GO
INSERT INTO dbo.[Object1] VALUES (1, 'Object 1 Value 1')
INSERT INTO dbo.[Object1] VALUES (2, 'Object 1 Value 2')
INSERT INTO dbo.[Object1] VALUES (3, 'Object 1 Value 3')
GO
INSERT INTO dbo.[Object2] VALUES (10, 1, 'Object 2 Value 1')
INSERT INTO dbo.[Object2] VALUES (20, 1, 'Object 2 Value 2')
INSERT INTO dbo.[Object2] VALUES (30, 2, 'Object 2 Value 3')
GO
INSERT INTO dbo.[Object3] VALUES (100, 10, 'Object 3 Value 1')
INSERT INTO dbo.[Object3] VALUES (200, 10, 'Object 3 Value 2')
INSERT INTO dbo.[Object3] VALUES (300, 30, 'Object 3 Value 3')
GO
SELECT
*
FROM
[Object1]
LEFT JOIN
[Object2] AS Object2s ON [Object1].Object1Id = [Object2s].Object1Id
LEFT JOIN
[Object3] AS Object3s ON [Object2s].Object2Id = [Object3s].Object2Id
WHERE
[Object1].Object1Id = 1
FOR
JSON AUTO,WITHOUT_ARRAY_WRAPPER
结果是 JSON,然后很容易将其反序列化为您想要的 class:
class Program
{
class Object1 {
public int Object1Id;
public List<Object2> Object2s;
}
class Object2 {
public int Object2Id;
public List<Object3> Object3s;
}
class Object3 {
public int Object3Id;
}
static void Main(string[] args)
{
using(var conn = new SqlConnection("Data Source=localhost; Initial Catalog=tempdb; Integrated Security=SSPI"))
{
var json = conn.ExecuteScalar<string>(@"
SELECT
*
FROM
[Object1]
LEFT JOIN
[Object2] AS Object2s ON [Object1].Object1Id = [Object2s].Object1Id
LEFT JOIN
[Object3] AS Object3s ON [Object2s].Object2Id = [Object3s].Object2Id
WHERE
[Object1].Object1Id = 1
FOR
JSON AUTO,WITHOUT_ARRAY_WRAPPER
");
var result = JsonConvert.DeserializeObject<Object1>(json.Replace("\"", "'"));
Console.WriteLine(result.Object2s.Count);
}
}
}
表演也很不错
在 Dapper 中,映射和对象包含列表并且每个列表项都有自己的列表的最佳方式是什么?
class Object1 {
int Object1Id;
List<Object2> object2s;
}
class Object2 {
int Object2Id;
List<Object3> object3s;
}
class Object3 {
int Object3Id;
}
这是我想使用的SQL
SELECT *
FROM [Object1] o1
left join [Object2] o2 on o1.Object1Id = o2.Object1Id
left join [Object3] o3 on o2.Object2Id = o3.Object2Id
使用左连接,因为 Object1 可能没有 Object2,而 Object2 可能没有任何 Object3
我考虑过使用
connection.Query<Object1, Object2, Object3, Object1>
但是在字典中跟踪字典以将它们添加到列表中似乎需要很多行代码。
使用 QueryMultiple 会更好吗?
你完全正确:这种父子处理不是 dapper 现在处理得很好的场景。如果它这样做了就好了,但它根本不是做某事的首要任务。
您可以选择两种不雅的解决方案。我个人认为 QueryMultiple
方法可能更简洁。
如果您使用 SQL Server 2016 或更高版本,我会选择 JSON。您可以 return 将数据作为 JSON 文档,如下所示:
USE tempdb
GO
DROP TABLE IF EXISTS dbo.[Object1]
DROP TABLE IF EXISTS dbo.[Object2]
DROP TABLE IF EXISTS dbo.[Object3]
GO
CREATE TABLE dbo.[Object1] ([Object1Id] INT PRIMARY KEY, [Value1] NVARCHAR(100));
CREATE TABLE dbo.[Object2] ([Object2Id] INT PRIMARY KEY, [Object1Id] INT, [Value2] NVARCHAR(100));
CREATE TABLE dbo.[Object3] ([Object3Id] INT PRIMARY KEY, [Object2Id] INT, [Value3] NVARCHAR(100));
GO
INSERT INTO dbo.[Object1] VALUES (1, 'Object 1 Value 1')
INSERT INTO dbo.[Object1] VALUES (2, 'Object 1 Value 2')
INSERT INTO dbo.[Object1] VALUES (3, 'Object 1 Value 3')
GO
INSERT INTO dbo.[Object2] VALUES (10, 1, 'Object 2 Value 1')
INSERT INTO dbo.[Object2] VALUES (20, 1, 'Object 2 Value 2')
INSERT INTO dbo.[Object2] VALUES (30, 2, 'Object 2 Value 3')
GO
INSERT INTO dbo.[Object3] VALUES (100, 10, 'Object 3 Value 1')
INSERT INTO dbo.[Object3] VALUES (200, 10, 'Object 3 Value 2')
INSERT INTO dbo.[Object3] VALUES (300, 30, 'Object 3 Value 3')
GO
SELECT
*
FROM
[Object1]
LEFT JOIN
[Object2] AS Object2s ON [Object1].Object1Id = [Object2s].Object1Id
LEFT JOIN
[Object3] AS Object3s ON [Object2s].Object2Id = [Object3s].Object2Id
WHERE
[Object1].Object1Id = 1
FOR
JSON AUTO,WITHOUT_ARRAY_WRAPPER
结果是 JSON,然后很容易将其反序列化为您想要的 class:
class Program
{
class Object1 {
public int Object1Id;
public List<Object2> Object2s;
}
class Object2 {
public int Object2Id;
public List<Object3> Object3s;
}
class Object3 {
public int Object3Id;
}
static void Main(string[] args)
{
using(var conn = new SqlConnection("Data Source=localhost; Initial Catalog=tempdb; Integrated Security=SSPI"))
{
var json = conn.ExecuteScalar<string>(@"
SELECT
*
FROM
[Object1]
LEFT JOIN
[Object2] AS Object2s ON [Object1].Object1Id = [Object2s].Object1Id
LEFT JOIN
[Object3] AS Object3s ON [Object2s].Object2Id = [Object3s].Object2Id
WHERE
[Object1].Object1Id = 1
FOR
JSON AUTO,WITHOUT_ARRAY_WRAPPER
");
var result = JsonConvert.DeserializeObject<Object1>(json.Replace("\"", "'"));
Console.WriteLine(result.Object2s.Count);
}
}
}
表演也很不错