odata如何知道ID是哪个属性？

Question

In the following example russelwhyte is the id, but how does the provider know to map it to the UserName property?

    URL: http://services.odata.org/V4/TripPinServiceRW/People?$format=application/json;odata.metadata=full
Response:
{
    @odata.context: "http://services.odata.org/V4/(S(ck3fzk3dze0kmzjcruxiz31i))/TripPinServiceRW/$metadata#People",
    @odata.nextLink: "http://services.odata.org/V4/TripPinServiceRW/People?%24format=application%2fjson%3bodata.
    metadata%3dfull&%24skiptoken=8",
    value:
    [
        {
            @odata.type: "#Microsoft.OData.SampleService.Models.TripPin.Person",
            @odata.id: "http://services.odata.org/V4/TripPinServiceRW/People('russellwhyte')",
            @odata.etag: "W/"08D17DBDFB9CCAAC"",
            @odata.editLink: "http://services.odata.org/V4/TripPinServiceRW/People('russellwhyte')",
            UserName: "russellwhyte",
            FirstName: "Russell",
            LastName: "Whyte",
            ...
            Friends@odata.associationLink: "http://services.odata.org/V4/TripPinServiceRW/People('russellwhyte')/Friends/$ref",
            Friends@odata.navigationLink: "http://services.odata.org/V4/TripPinServiceRW/People('russellwhyte')/Friends",
            ...
        },
        ...
    ]
}

Answer 1

通过重写基类EntitySetController GetEntityByKey

Answer 2

Query the metadata document, you can get the model schema for the service, and in which you can find which properties are the keys/IDs.

For example:

GET: http://services.odata.org/V4/(S(ksn5grnrgbebt44osly5z2vr))/TripPinServiceRW/ $metadata

<EntityType Name="Person" OpenType="true">
  <Key>
    <PropertyRef Name="UserName"/>
  </Key>
  <Property Name="UserName" Type="Edm.String" Nullable="false">
    <Annotation Term="Org.OData.Core.V1.Permissions">
      <EnumMember>Org.OData.Core.V1.Permission/Read</EnumMember>
    </Annotation>
  </Property>
  <Property Name="FirstName" Type="Edm.String" Nullable="false"/>
  <Property Name="LastName" Type="Edm.String" Nullable="false"/>
  <Property Name="Emails" Type="Collection(Edm.String)"/>
  <Property Name="AddressInfo" Type="Collection(Microsoft.OData.SampleService.Models.TripPin.Location)"/>
  <Property Name="Gender" Type="Microsoft.OData.SampleService.Models.TripPin.PersonGender"/>
  <Property Name="Concurrency" Type="Edm.Int64" Nullable="false">
    <Annotation Term="Org.OData.Core.V1.Computed" Bool="true"/>
  </Property>
  <NavigationProperty Name="Friends" Type="Collection(Microsoft.OData.SampleService.Models.TripPin.Person)"/>
  <NavigationProperty Name="Trips" Type="Collection(Microsoft.OData.SampleService.Models.TripPin.Trip)" ContainsTarget="true"/>
  <NavigationProperty Name="Photo" Type="Microsoft.OData.SampleService.Models.TripPin.Photo"/>
</EntityType>