使用左连接获得不适当的输出

我正在尝试获取变体列表，并且对于每个变体都获取所有subvariants list而不管子变量在哪里落入特定Test say 100这是样本数据：

 Id TestId SourceSubVariantId TargetSubVariantId DiffPerc 114 100 66 67 100.00 115 100 67 68 100.00 116 100 70 71 99.99 

变体1有3个子变量 ：

 Id=66,Name=Abc Id=68,Name=Pqr Id=69,Name=xyz 

变体2有3个子变量 ：

 Id=70,Name=lmn Id=71,Name=xxx Id=72,Name=hhh 

但是在我的输出中注意到Variant1 CustomSubvariantList Variants 2 subvariants list所有Id as 0 ：

数据模型：

 public class Variants { public int Id { get; set; } public string Name { get; set; } public string Type { get; set; } public virtual ICollection SubVariants { get; set; } } public class SubVariants { public int Id { get; set; } public int VariantId { get; set; } public string Name { get; set; } public virtual Variants Variants { get; set; } public virtual ICollection TestOperation { get; set; } public virtual ICollection TestOperation1 { get; set; } } public class TestOperation { public int Id { get; set; } public Nullable TestId { get; set; } public int SourceSubVariantId { get; set; } public int TargetSubVariantId { get; set; } public decimal DiffPerc { get; set; } public virtual SubVariants SubVariants { get; set; } public virtual SubVariants SubVariants1 { get; set; } public virtual Test Test { get; set; } } 

查询：

 int testId=100; var query = from v in context.Variants where v.Type == "Add" select new { ParentVariant = v.Name, Type = v.Method, CustomSubvariantList = ( from svName in context.SubVariants.Select(sv => sv.Name).Distinct() join x in ( from sv in v.SubVariants from to in sv.TestOperation where to.TestId == testId orderby sv.Id select new { sv.Name, to.DiffPerc, SourceId = (int?)to.SubVariants.Id, TargetID=(int?)to.SubVariants1.Id } ) on svName equals x.Name into g from x in g.DefaultIfEmpty() orderby x.SourceId select new { SourceId=x.SourceId ?? 0, TargetId=x.TargetID ?? 0, Name = svName, DiffPerc = x.DiffPerc } ).ToList() }; 

更新： 根据评论，这是样本输入和预期输出：

情况1 ： 当所有父变体中的子变量名称不同时

变种：

 Id Name Type CategoryId 11 Variant1 Add 1 12 Variant2 Add 1 13 Variant3 Add 1 14 Variant4 Add 1 

子变体：

 Id VariantId Name 66 11 Abc 67 11 PQR 68 11 Xyz 70 12 lmn 71 12 xxx 72 12 hhh 

测试操作：

 Id TestId SourceSubVariantId TargetSubVariantId DiffPerc 114 100 66 67 10.00 115 100 67 68 20.00 114 100 70 71 40.00 115 100 71 72 50.00 

预期产量 ：

情况2 ： 当所有父变体中的子变量名称相同时：

子变体：

 Id VariantId Name 66 11 Abc 67 11 PQR 68 11 Xyz 70 12 Abc 71 12 PQR 72 12 Xyz 

预期产出 ：

Answer 1

我们有一些关于聊天的讨论，直到我明白你想要什么。

这是代码：

  class Program { static void Main(string[] args) { VariantsEntities db=new VariantsEntities(); var queryResult = db.Variants.AsEnumerable().Select(x => new PageViewModel { ParentVariant = x.Name, Type = x.Type, CustomSubvariantList = GetCustomSubVariants(x.Id,db).ToList() }).ToList(); var jsonObj = JsonConvert.SerializeObject(queryResult); Console.WriteLine(jsonObj); Console.ReadKey(); } private static IEnumerable GetCustomSubVariants(int variantId, VariantsEntities db) { var subVariants = db.SubVariants.ToList(); foreach (var subVariant in subVariants) { var obj=new Customsubvariantlist(); obj.Name = subVariant.Name; var testOpTarget = db.TestOperations .FirstOrDefault(x => x.TargetSubVariantId == subVariant.Id); var testOpSource = db.TestOperations .FirstOrDefault(x => x.SourceSubVariantId == subVariant.Id); if (subVariant.VariantId == variantId) { obj.Value = testOpTarget == null ? testOpSource?.SourceValue : testOpTarget?.TargetValue; obj.DiffPerc = testOpTarget?.DiffPerc; } else { obj.Value = null; obj.DiffPerc = null; } yield return obj; } } } 

你只需要替换DbContext名称，然后测试它。

这是结果：

  [ { "ParentVariant": "Variant1", "Type": "Add", "CustomSubvariantList": [ { "Name": "Abc", "Value": 200, "DiffPerc": null }, { "Name": "Pqr", "Value": 300, "DiffPerc": 100.0 }, { "Name": "xyz", "Value": 500, "DiffPerc": 200.0 }, { "Name": "lmn", "Value": null, "DiffPerc": null }, { "Name": "xxx", "Value": null, "DiffPerc": null }, { "Name": "hhh", "Value": null, "DiffPerc": null } ] }, { "ParentVariant": "Variant2", "Type": "Add", "CustomSubvariantList": [ { "Name": "Abc", "Value": null, "DiffPerc": null }, { "Name": "Pqr", "Value": null, "DiffPerc": null }, { "Name": "xyz", "Value": null, "DiffPerc": null }, { "Name": "lmn", "Value": 1000, "DiffPerc": null }, { "Name": "xxx", "Value": 2000, "DiffPerc": 1000.0 }, { "Name": "hhh", "Value": 4000, "DiffPerc": 2000.0 } ] } ] 

从这里您可以下载示例项目。 这个项目是用你发给我的样本数据库完成的，所以是数据库优先，有些道具或表可能有不同的名字，请在项目中移动代码之前检查一下。

基本上我做了什么：

1. 创建了一个新的控制台app项目

2. 我从你的json对象中获取了模型（我复制了json对象并将其放在一个类中，使用（vs菜单）Edit – > Past Special – > Past JSON as Classes。

3. 由于你想要每个Varian所有SubVariants ，我创建了一个单独的方法来处理你创建CustomSubVariantList的规则。 在这个方法中，我迭代抛出所有SubVariants，我根据你的条件创建了对象。

更新：您的解决方案在一个查询中：

 static void Main(string[] args) { VariantsEntities db = new VariantsEntities(); var result = from x in db.Variants select new PageViewModel { ParentVariant = x.Name, Type = x.Type, CustomSubvariantList = (from z in db.SubVariants let testOpTarget=z.TestOperations1 .FirstOrDefault(q=>q.TargetSubVariantId==z.Id) let testOpSource=z.TestOperations .FirstOrDefault(q=>q.SourceSubVariantId==z.Id) select new Customsubvariantlist { Name = z.Name, Value = x.Id==z.VariantId? testOpTarget.TargetValue?? testOpSource.SourceValue:null, DiffPerc = x.Id==z.VariantId? testOpTarget.DiffPerc:null }).ToList() }; var json = JsonConvert.SerializeObject(result.ToList()); Console.WriteLine(json); Console.ReadKey(); } 

此查询产生与上述方法相同的结果。 如果您需要，请告诉我！

更新：这是案例2的查询

  var result = from x in db.Variants select new PageViewModel { ParentVariant = x.Name, Type = x.Type, CustomSubvariantList = (from z in db.SubVariants.GroupBy(g => g.Name) .Select(g => g.FirstOrDefault(d => d.VariantId == x.Id) ?? g.FirstOrDefault()) let testOpTarget = z.TestOperations1 .FirstOrDefault(q => q.TargetSubVariantId == z.Id) let testOpSource = z.TestOperations .FirstOrDefault(q => q.SourceSubVariantId == z.Id) select new Customsubvariantlist { Name = z.Name, SubVariantId = z.Id, CombineName =(z.TestOperations.Any() || z.TestOperations1.Any())? testOpTarget.TargetValue.HasValue? testOpTarget.SubVariant.Name+" to "+testOpTarget.SubVariant1.Name : null: "Undefined", Value = x.Id == z.VariantId ? testOpTarget.TargetValue ?? testOpSource.SourceValue : null, DiffPerc = x.Id == z.VariantId ? testOpTarget.DiffPerc : null }).OrderBy(k => k.SubVariantId).ToList() }; 

Answer 2

这是您的查询的“变体”..它提取了每个Variant(s)所有SubVariants ，因为它们在表SubVariants中（通过其自动化的Sql Server Identity Id），不管涉及的TestOperation如何，并避免重复作为您的预期输出。

遗憾的是，不可能始终将所有子变量指定为source和tartget子变量，因为此信息取决于testoperation，实际上testop决定子变量是“source”还是“target”。 因此，如果某些子变量未包含在testoperations记录/实体中，那么它们就不能作为源或目标出现..一种解决方法可能是附加，在返回的匿名类型的“Name”属性旁边，也是“Id SubVar”

我添加了2个DTO，因为entity framework不允许使用distinct().ToList()方法来保留顺序并应用自定义的不同规则，所以我添加了一个步骤，通过dto对象在链接到对象的链接到EF传递这种方式可以应用不同的自定义规则。

  public class CustomerVariantDTO { public String Type; public String ParentVariant; public IEnumerable CustomSubvariantList; } public class CustomerSubVariantDTO { public int? VariantId; public int? SubVariantId; public int? SourceId; public int? TargetId; public String Name; public Decimal? DiffPerc; } sealed class CustomerSubVariantDTOComparer : IEqualityComparer { public int GetHashCode(CustomerSubVariantDTO obj) { return 0; } public bool Equals(CustomerSubVariantDTO x, CustomerSubVariantDTO y) { return x.SourceId == y.SourceId && x.TargetId == y.TargetId && x.Name == y.Name && x.DiffPerc == y.DiffPerc; } } public void DoTestOfCustomerVariantDTO() { int testId = 1; using (var context = new VariantsEntities()) { var query = (from v in context.Variants where v.Type == "Add" select new CustomerVariantDTO { ParentVariant = v.Name, Type = v.Type, CustomSubvariantList = ( from sv in context.SubVariants.Select(sv => sv) join x in ( from svparent in v.SubVariants from to in svparent.TestOperation where to.TestId == testId select new { svparent.Name, to.DiffPerc, SourceId = (int?)to.SubVariants.Id ?? 0, TargetId = (int?)to.SubVariants1.Id ?? 0 } ) on sv.Name equals x.Name into g from x in g.DefaultIfEmpty() select new CustomerSubVariantDTO{ VariantId = sv.VariantId, SubVariantId = sv.Id, SourceId = (int?)x.SourceId ?? sv.TestOperation.Select(to => to.SourceSubVariantId).FirstOrDefault(), TargetId = (int?)x.TargetId ?? sv.TestOperation.Select(to => to.TargetSubVariantId).FirstOrDefault(), Name = sv.Name, DiffPerc = x.DiffPerc } ).OrderBy(csv => new { csv.VariantId, csv.SubVariantId }) }).ToList(); var listCustomVariants = query.Select(v => new{ Type = v.Type, ParentVariant = v.ParentVariant, CustomSubvariantList = v.CustomSubvariantList.Distinct(new CustomerSubVariantDTOComparer()).ToList() }); foreach (var item in listCustomVariants){ Console.WriteLine($"Type: {item.Type} - ParentVariant: {item.ParentVariant} "); foreach (var csubvar in item.CustomSubvariantList) Console.WriteLine($"SourceId: {csubvar.SourceId} - TargetiId: {csubvar.TargetId} - NAme: {csubvar.Name} - DiffPerc: {csubvar.DiffPerc} "); } } }