The EDM instance of type '[type Nullable=True]' is missing the property 'id'.

Assemblies affected
Microsoft.AspNetCore.OData Version="8.1.1"

Describe the bug
I'm getting:

An unhandled exception has occurred while executing the request.
      System.InvalidOperationException: The EDM instance of type '[ODataError.Domain.Taxonomies.Country Nullable=True]' is missing the property 'id'.
         at Microsoft.AspNetCore.OData.Formatter.ResourceContext.GetPropertyValue(String propertyName)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateStructuralProperty(IEdmStructuralProperty structuralProperty, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateStructuralPropertyBag(SelectExpandNode selectExpandNode, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateResource(SelectExpandNode selectExpandNode, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.WriteResourceAsync(Object graph, ODataWriter writer, ODataSerializerContext writeContext, IEdmTypeReference expectedType)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.WriteObjectInlineAsync(Object graph, IEdmTypeReference expectedType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteResourceSetAsync(IEnumerable enumerable, IEdmTypeReference resourceSetType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteObjectInlineAsync(Object graph, IEdmTypeReference expectedType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteObjectAsync(Object graph, Type type, ODataMessageWriter messageWriter, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.ODataOutputFormatterHelper.WriteToStreamAsync(Type type, Object value, IEdmModel model, ODataVersion version, Uri baseAddress, MediaTypeHeaderValue contentType, HttpRequest request, IHeaderDictionary requestHeaders, IODataSerializerProvider serializerProvider)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Microsoft.AspNetCore.OData.Query.ODataQueryRequestMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.OData.Routing.ODataRouteDebugMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Reproduce steps

I made a small project where I include the minimum necessary of my code to reproduce it:

• download ODataError.zip
• Make a request to [GET] https://localhost:7066/odata/v1/countries

Data Model

public abstract class Entity<TId>
{
    [Key]
    public TId Id { get; set; }

    public override bool Equals(object obj) {...}

    public override int GetHashCode() {...}

    public static bool operator ==(Entity<TId> a, Entity<TId> b) {...}

    public static bool operator !=(Entity<TId> a, Entity<TId> b) {...}
}

public abstract class AuditableEntity<T> : Entity<T>
{
    public AuditableEntity() {}
    public AuditableEntity(T id) {...}
    
    public DateTimeOffset CreatedOn { get; set; }
    public Guid CreatedById { get; set; }
    public string CreatedByDisplayName { get; set; }

    public DateTimeOffset? ModifiedOn { get; set; }
    public Guid? ModifiedById { get; set; }
    public string ModifiedByDisplayName { get; set; }

    public DateTime Timestamp { get; set; }


    public virtual void UpdateCreationMetadata(Guid? userId = null, string displayName = null, DateTimeOffset? createdOn = null) {...}
    public virtual void UpdateModificationMetadata(Guid? userId = null, string displayName = null, DateTimeOffset? updatedOn = null) {...}
}

public class Country : AuditableEntity<int>
{
    [JsonConstructor]
    public Country() {...}
    public Country(int id, string name, string iso2, string iso3, string phoneCode) : base(id) {...}

    public string Name { get; set; }
    public string Iso2 { get; set; }
    public string Iso3 { get; set; }
    public string PhoneCode { get; set; }
}

public class Language : AuditableEntity<int>
{
    [JsonConstructor]
    public Language() {...}
    public Language(int id, string name, string code) : base(id) {...}

    public string Name { get; set; }
    public string Code { get; set; }
}

public class Methodology : AuditableEntity<Guid>
{
    [JsonConstructor]
    public Methodology() {...}
    public Methodology(Guid id, string name) : base(id) {...}

    public string Name { get; set; }
}

EDM (CSDL) Model

<?xml version="1.0" encoding="utf-8"?>
<edmx:Edmx Version="4.0" xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx">
    <edmx:DataServices>
        <Schema Namespace="ODataError.Domain.Taxonomies" xmlns="http://docs.oasis-open.org/odata/ns/edm">
            <EntityType Name="Country">
                <Key>
                    <PropertyRef Name="id" />
                </Key>
                <Property Name="id" Type="Edm.Int32" Nullable="false" />
                <Property Name="name" Type="Edm.String" />
                <Property Name="iso2" Type="Edm.String" />
                <Property Name="iso3" Type="Edm.String" />
                <Property Name="phoneCode" Type="Edm.String" />
                <Property Name="createdOn" Type="Edm.DateTimeOffset" Nullable="false" />
                <Property Name="createdById" Type="Edm.Guid" Nullable="false" />
                <Property Name="createdByDisplayName" Type="Edm.String" />
                <Property Name="modifiedOn" Type="Edm.DateTimeOffset" />
                <Property Name="modifiedById" Type="Edm.Guid" />
                <Property Name="modifiedByDisplayName" Type="Edm.String" />
                <Property Name="timestamp" Type="Edm.DateTimeOffset" Nullable="false" />
            </EntityType>
            <EntityType Name="Language">
                <Key>
                    <PropertyRef Name="id" />
                </Key>
                <Property Name="id" Type="Edm.Int32" Nullable="false" />
                <Property Name="name" Type="Edm.String" />
                <Property Name="code" Type="Edm.String" />
                <Property Name="createdOn" Type="Edm.DateTimeOffset" Nullable="false" />
                <Property Name="createdById" Type="Edm.Guid" Nullable="false" />
                <Property Name="createdByDisplayName" Type="Edm.String" />
                <Property Name="modifiedOn" Type="Edm.DateTimeOffset" />
                <Property Name="modifiedById" Type="Edm.Guid" />
                <Property Name="modifiedByDisplayName" Type="Edm.String" />
                <Property Name="timestamp" Type="Edm.DateTimeOffset" Nullable="false" />
            </EntityType>
            <EntityType Name="Methodology">
                <Key>
                    <PropertyRef Name="id" />
                </Key>
                <Property Name="id" Type="Edm.Guid" Nullable="false" />
                <Property Name="name" Type="Edm.String" />
                <Property Name="createdOn" Type="Edm.DateTimeOffset" Nullable="false" />
                <Property Name="createdById" Type="Edm.Guid" Nullable="false" />
                <Property Name="createdByDisplayName" Type="Edm.String" />
                <Property Name="modifiedOn" Type="Edm.DateTimeOffset" />
                <Property Name="modifiedById" Type="Edm.Guid" />
                <Property Name="modifiedByDisplayName" Type="Edm.String" />
                <Property Name="timestamp" Type="Edm.DateTimeOffset" Nullable="false" />
            </EntityType>
        </Schema>
        <Schema Namespace="Default" xmlns="http://docs.oasis-open.org/odata/ns/edm">
            <EntityContainer Name="Container">
                <EntitySet Name="Countries" EntityType="ODataError.Domain.Taxonomies.Country" />
                <EntitySet Name="Languages" EntityType="ODataError.Domain.Taxonomies.Language" />
                <EntitySet Name="Methodologies" EntityType="ODataError.Domain.Taxonomies.Methodology" />
            </EntityContainer>
        </Schema>
    </edmx:DataServices>
</edmx:Edmx>

model built using:

public static IEdmModel GetODataModel()
{
    // Create the service EDM model.
    var modelBuilder = new ODataConventionModelBuilder()
                            .EnableLowerCamelCase();

    modelBuilder.EntitySet<Country>("Countries");
    modelBuilder.EntityType<Country>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Language>("Languages");
    modelBuilder.EntityType<Language>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Methodology>("Methodologies");
    modelBuilder.EntityType<Methodology>().HasKey(x => x.Id);

    return modelBuilder.GetEdmModel();
}

controller example:

[ApiController]
[Route("api/v1/{controller}")]
[AllowAnonymous]
public class CountriesController : ODataController
{
    List<Country> _countries = new List<Country> { new Country(1, "spain", "sp", "spa", "34"), new Country(2, "usa", "us", "usa", "1") };


    public CountriesController()
    {
    }

    [HttpGet]
    [EnableQuery]
    public async Task<ActionResult<IQueryable<Country>>> Get()
    {
        return Ok(_countries);
    }

    [HttpGet("{key}")]
    public async Task<ActionResult<Country>> Get([FromODataUri] int key)
    {
        var result = _countries.FirstOrDefault(x => x.Id == key);
        if (result is object) return result;
        return NotFound();
    }
}

Request/Response
[GET] https://localhost:7066/odata/v1/countries

      System.InvalidOperationException: The EDM instance of type '[ODataError.Domain.Taxonomies.Country Nullable=True]' is missing the property 'id'.
         at Microsoft.AspNetCore.OData.Formatter.ResourceContext.GetPropertyValue(String propertyName)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateStructuralProperty(IEdmStructuralProperty structuralProperty, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateStructuralPropertyBag(SelectExpandNode selectExpandNode, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.CreateResource(SelectExpandNode selectExpandNode, ResourceContext resourceContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.WriteResourceAsync(Object graph, ODataWriter writer, ODataSerializerContext writeContext, IEdmTypeReference expectedType)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSerializer.WriteObjectInlineAsync(Object graph, IEdmTypeReference expectedType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteResourceSetAsync(IEnumerable enumerable, IEdmTypeReference resourceSetType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteObjectInlineAsync(Object graph, IEdmTypeReference expectedType, ODataWriter writer, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.Serialization.ODataResourceSetSerializer.WriteObjectAsync(Object graph, Type type, ODataMessageWriter messageWriter, ODataSerializerContext writeContext)
         at Microsoft.AspNetCore.OData.Formatter.ODataOutputFormatterHelper.WriteToStreamAsync(Type type, Object value, IEdmModel model, ODataVersion version, Uri baseAddress, MediaTypeHeaderValue contentType, HttpRequest request, IHeaderDictionary requestHeaders, IODataSerializerProvider serializerProvider)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
         at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
         at Microsoft.AspNetCore.OData.Query.ODataQueryRequestMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.OData.Routing.ODataRouteDebugMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Watch.BrowserRefresh.BrowserRefreshMiddleware.InvokeAsync(HttpContext context)
         at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.ProcessRequests[TContext](IHttpApplication`1 application)

Expected behavior
the odata response (like [GET] https://localhost:7066/odata/v1/languages)

Additional context
First I added Country and it worked, then I added Language and Methodology and it stopped working. Looking at other issues on the internet (like https://github.com/OData/WebApi/issues/1625) I think it is related to the use of .EnableLowerCamelCase() and .HasKey(x => x.Id).

this doesnt work:

public static IEdmModel GetODataModel()
{
    // Create the service EDM model.
    var modelBuilder = new ODataConventionModelBuilder()
                            .EnableLowerCamelCase();

    modelBuilder.EntitySet<Country>("Countries");
    modelBuilder.EntityType<Country>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Language>("Languages");
    modelBuilder.EntityType<Language>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Methodology>("Methodologies");
    modelBuilder.EntityType<Methodology>().HasKey(x => x.Id);

    return modelBuilder.GetEdmModel();
}

this work (but there are entities missing as expected):

public static IEdmModel GetODataModel()
{
    // Create the service EDM model.
    var modelBuilder = new ODataConventionModelBuilder()
                            .EnableLowerCamelCase();

    modelBuilder.EntitySet<Country>("Countries");
    modelBuilder.EntityType<Country>().HasKey(x => x.Id);

    /*modelBuilder.EntitySet<Language>("Languages");
    modelBuilder.EntityType<Language>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Methodology>("Methodologies");
    modelBuilder.EntityType<Methodology>().HasKey(x => x.Id);*/

    return modelBuilder.GetEdmModel();
}

this work (but I like to define here my entities and do not rely on conventions on the model class):

public static IEdmModel GetODataModel()
{
    // Create the service EDM model.
    var modelBuilder = new ODataConventionModelBuilder()
                            .EnableLowerCamelCase();

    modelBuilder.EntitySet<Country>("Countries");
    //modelBuilder.EntityType<Country>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Language>("Languages");
    //modelBuilder.EntityType<Language>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Methodology>("Methodologies");
    //modelBuilder.EntityType<Methodology>().HasKey(x => x.Id);

    return modelBuilder.GetEdmModel();
}

this work (but I need to use lower case):

public static IEdmModel GetODataModel()
{
    // Create the service EDM model.
    var modelBuilder = new ODataConventionModelBuilder();
                           // .EnableLowerCamelCase();

    modelBuilder.EntitySet<Country>("Countries");
    modelBuilder.EntityType<Country>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Language>("Languages");
    modelBuilder.EntityType<Language>().HasKey(x => x.Id);

    modelBuilder.EntitySet<Methodology>("Methodologies");
    modelBuilder.EntityType<Methodology>().HasKey(x => x.Id);

    return modelBuilder.GetEdmModel();
}

[GET] https://localhost:7066/odata/v1/languages and [GET] https://localhost:7066/odata/v1/methodologies work but [GET] https://localhost:7066/odata/v1/countries doesnt

Screenshots

from https://localhost:7066/$odata