我有一个这样的集合:

[{
  "_id": 1,
  "OtherProperties": 100
  "PersonInventory": [{
    "FirstName": "Joe",
    "MiddleName": "Bob",
    "LastName": "Blogs",
    "PersonId": 1
  }]
},{
  "_id": 2,
  "OtherProperties": 1005
  "PersonInventory": [{
    "FirstName": "Joe",
    "MiddleName": "Bob",
    "LastName": "Blogs",
    "PersonId": 1
  }]
}]

我正在尝试使用此处较新的类型推断 mongodb c# 驱动程序语法来选择根文档中的所有唯一人员。

到目前为止已经试过了，但收到错误消息说该方法不可用(我认为这与分组有关)，谁能告诉我哪里出错了？

collection.Aggregate()
  .Match(m => m.PersonInventory.Count > o)
  .Unwind<RootDoc, Person>(t => t.PersonInventory)
  .Group(k => k.PersonId, g => g.First())
  .ToListAsync();

模型:

public class Person
{
  [BsonId]
  public long PersonId { get; set; }
  public string FirstName { get; set; }
  public string MiddleName { get; set; }
  public string LastName { get; set; }
}

public class RootDoc
{
  public long Id{ get; set; }
  //more props
  public IList<Person> PersonInventory { get; set; }
}

仅供引用，错误消息是不支持指定的方法。。

堆栈跟踪:

   at MongoDB.Driver.Linq.Processors.AccumulatorBinder.GetAccumulatorArgument(Expression node)
   at MongoDB.Driver.Linq.Processors.AccumulatorBinder.TryGetAccumulatorTypeAndArgument(PipelineExpression node, AccumulatorType& accumulatorType, Expression& argument)
   at MongoDB.Driver.Linq.Processors.AccumulatorBinder.VisitPipeline(PipelineExpression node)
   at MongoDB.Driver.Linq.Expressions.PipelineExpression.Accept(ExtensionExpressionVisitor visitor)
   at MongoDB.Driver.Linq.Expressions.ExtensionExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at MongoDB.Driver.Linq.Processors.EmbeddedPipeline.EmbeddedPipelineBinder.Bind(Expression node, IBindingContext parent)
   at MongoDB.Driver.Linq.Processors.SerializationBinder.BindEmbeddedPipeline(MethodCallExpression node)
   at MongoDB.Driver.Linq.Processors.SerializationBinder.VisitMethodCall(MethodCallExpression node)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at MongoDB.Driver.Linq.Processors.SerializationBinder.Visit(Expression node)
   at MongoDB.Driver.Linq.Translators.AggregateGroupTranslator.BindGroup[TKey,TDocument,TResult](PipelineBindingContext bindingContext, Expression`1 groupProjector, IBsonSerializer`1 parameterSerializer, Expression keySelector)
   at MongoDB.Driver.Linq.Translators.AggregateGroupTranslator.Translate[TKey,TDocument,TResult](Expression`1 idProjector, Expression`1 groupProjector, IBsonSerializer`1 parameterSerializer, IBsonSerializerRegistry serializerRegistry, ExpressionTranslationOptions translationOptions)
   at MongoDB.Driver.GroupExpressionProjection`3.Render(IBsonSerializer`1 documentSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.PipelineStageDefinitionBuilder.<>c__DisplayClass19_0`2.<Group>b__0(IBsonSerializer`1 s, IBsonSerializerRegistry sr)
   at MongoDB.Driver.DelegatedPipelineStageDefinition`2.Render(IBsonSerializer`1 inputSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.AppendedStagePipelineDefinition`3.Render(IBsonSerializer`1 inputSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.MongoCollectionImpl`1.<AggregateAsync>d__22`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.MongoCollectionImpl`1.<UsingImplicitSessionAsync>d__101`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.IAsyncCursorSourceExtensions.<ToListAsync>d__16`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at App.Application.Services.CacheSyncService.<GetAllCrewAsync>d__9.MoveNext() in C:\Users\gdp\Sites\app\Services\CacheSyncService.cs:line 77
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at App.Application.Services.Sync.ReferenceDataSyncService.<ResolveCrewReferences>d__6.MoveNext() in C:\Users\gdp\Sites\app\Services\Sync\ReferenceDataSyncService.cs:line 46
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at App.API.Controllers.DataSyncController.<ResolveCrewReferences>d__3.MoveNext() in C:\Users\gdp\Sites\app\Controllers\DataSyncController.Triggers.cs:line 87
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.TaskHelpersExtensions.<CastToObject>d__1`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__6.MoveNext()

最佳答案

我在 mongodb Jira 页面上做了一些挖掘，看起来不支持变量 $$ROOT，所以不支持上述查询。

关于c# - 带有 Group Unwind 和 Project 的 MongoDb C# 类型聚合，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57584337/