I'm getting this error when I try to GET an item from Mongo right after starting my API:

当我尝试在启动API后立即从Mongo获取项目时，收到以下错误：

Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
      An unhandled exception has occurred while executing the request.
      System.AggregateException: One or more errors occurred. (An error occurred while deserializing the Fields property of class divitiae_api.Models.App: Element 'AppRelationId' does not match any field or property of class divitiae_api.Models.FieldStructure.)

The item that I'm trying to get (called App) has the next structure:

我正在尝试获取的项(称为App)具有下一个结构：

public class App
    {
        [BsonId]
        public ObjectId Id { get; set; }
        public string StringId { get; set; } = string.Empty;
        public string AppName { get; set; } = string.Empty;
        public List<FieldStructure> Fields { get; set; } = new List<FieldStructure>();
        public List<ObjectId> Items { get; set; } = new List<ObjectId>();
    }

And the property that "fails" to be serialized is this one:

而“无法”序列化的属性是：

public class FieldStructure
    {
        public FieldStructure(string name, string type)
        {
                Name = name;
                Type = type;
                NameAsProperty = name.ToLower().Replace(" ", "_");
            
        }

        public FieldStructure() { }

        public string Name { get; set; } = string.Empty;
        public string NameAsProperty { get; set; } = string.Empty;
        public string Type { get; set; } = string.Empty;

    }

    public class FieldStructureRelation : FieldStructure
    {
        public FieldStructureRelation(FieldStructure fieldStructure, string appRelationId) 
            : base(fieldStructure.Name, fieldStructure.Type)
        {
            this.AppRelationId = appRelationId;
        }

        public FieldStructureRelation(string name, string type, string appRelationId) 
            : base(name, type) 
        {
            this.AppRelationId = appRelationId;
        }
        
        public FieldStructureRelation() { }

        public string AppRelationId { get; set; } = string.Empty;
    }

The App's "fields" property is basically a list of FieldStructure objects that can be both FieldStructures and FieldStructureRelations. I get no errors when inserting these type of lists as the app detects them as compatible for that same list.

App的“field”属性基本上是FieldStructure对象的列表，这些对象既可以是FieldStructures也可以是FieldStrucreRelationship。在插入这些类型的列表时，我没有收到任何错误，因为应用程序检测到它们与同一列表兼容。

The weird thing is that if I start the api and try to get one of these "App" objects, I get the error that I first showed saying that "FieldStructure" has no "AppRelationId" property (in this case, the system should detect it as a "FieldStructureRelation", not the other one). But, if I create an App with a mix of Fields being "FieldStructure" and "FieldStructureRelation", then every single GET request after this action is succesful.

奇怪的是，如果我启动api并尝试获取其中一个“App”对象，我会得到我第一次显示的错误，说“FieldStructure”没有“AppsourceId”属性（在这种情况下，系统应该将其检测为“FieldStructureRelation”，而不是另一个）。但是，如果我创建一个应用程序，其中混合了“FieldStructure”和“FieldStructureRelation”字段，那么在此操作之后的每个GET请求都是成功的。

I don't understand what is going on here, so any help is very much appreciated!

我不知道这里发生了什么，所以任何帮助都是非常感激的！