[英]Dapper receive List as object parameter from JOIN query
I have trouble using Dapper
when i want to map my object from database. 我想从数据库映射对象时使用Dapper
遇到麻烦。
class Set
{
public Guid Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public List<Guid> GeneratorsList { get; set; }
}
It contains a list so I've created separated table that holds it, like that 它包含一个列表,因此我创建了一个单独的表来保存它,像这样
CREATE TABLE [dbo].[Sets] (
[Id] UNIQUEIDENTIFIER NOT NULL,
[Name] VARCHAR (60) NOT NULL,
[Description] VARCHAR (60) NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
CREATE TABLE [dbo].[Set_Generator] (
[SetId] UNIQUEIDENTIFIER NOT NULL,
[GeneratorId] UNIQUEIDENTIFIER NOT NULL,
PRIMARY KEY CLUSTERED ([SetId] ASC, [GeneratorId] ASC),
FOREIGN KEY ([SetId]) REFERENCES [dbo].[Sets] ([Id]) ON DELETE CASCADE
);
And from those tables I want to retrieve correct Set object with minimum code effort. 从这些表中,我想以最少的代码工作量检索正确的Set对象。 I've tried to do join on them and strong type the result to Set
, but with no success. 我尝试加入它们并将结果强类型输入Set
,但是没有成功。
var result = conn.Query<Set>(@"SELECT [S].[Id], [S].[Name], [S].[Description], [SG].[GeneratorId] AS [GeneratorsList] FROM [Sets] AS [S] INNER JOIN [Set_Generator] AS [SG] ON [S].[Id] = [SG].[SetId];");
I'm aware that I could simply retrieve Set
from table and then add the GeneratorsList
from separate query, but I'm looking for a better solution. 我知道我可以简单地从表中检索Set
,然后从单独的查询中添加GeneratorsList
,但我正在寻找更好的解决方案。
var sets = conn.Query<Set>(@"SELECT * FROM [Sets];");
foreach(var set in sets)
{
var generators = conn.Query<Guid>(@"SELECT [GeneratorId] FROM [Set_Generator] WHERE [SetId]=@SetId", new { SetId = set.Id });
set.GeneratorsList = generators.ToList();
}
Is there a solution that require only one query ? 是否有只需要一个查询的解决方案?
Using the query you provided you may receive: 使用您提供的查询,您可能会收到:
internal class GeneratorSet
{
public Guid Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public Guid GeneratorId { get; set; }
}
And use linq
GroupBy
to construct the Set
object(-s): 并使用linq
GroupBy
构造Set
对象(-s):
var generatorSets = conn.Query<GeneratorSet>(@"SELECT [S].[Id], [S].[Name], [S].[Description], [SG].[GeneratorId] AS [GeneratorsList] FROM [Sets] AS [S] INNER JOIN [Set_Generator] AS [SG] ON [S].[Id] = [SG].[SetId];");;
var res = generatorSets.GroupBy(gen => gen.Id, p => p, (key, g) => new Set()
{ Id = key, Generators = g.Select(g => g.GeneratorId)});
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