I thought I understood from experience how to do many-to-one relationships and from the documentation how to attempt a many-to-many relationship. Unfortunately, things are not working at the moment. If I comment out the property/relationship State.Cities, remove the Association declaration from City.State, and comment out both sides of the many-to-many relationship between ZipCode and AreaCode then my website builds. If I do not, then during Domain.Build() I get:

Item with key 'Fields' was not found. You might have forgotten to apply [Field] attribute on property Fields.State. OR Field 'ZipCode.AreaCodes' is already paired with 'AreaCode.ZipCodes'. Please remove [Association] attribute at 'AreaCode.ZipCodes'. I am particularly confused as to why Country->States works but State->ZipCodes does not. I was trying to learn how to use a many-to-many relationship from linq-many-to-many-relationship topic @ support and documentation

I am working with a legacy database (DomainUpgradeMode.LegacyValidate) and there is no way around that. A partial excerpt of my code base, which I hope is the relevant part, is:

<TableMapping("tblCountries")>
<HierarchyRoot(), KeyGenerator(KeyGeneratorKind.None)>
Public Class Country Inherits Entity

    <Field(), Key()>
    Property ID As Integer

    <Field(Nullable:=False), FieldMapping("geoLocationID")>
    Property GeoLocation As GeoLocation

    <Field(), Association("Country")>
    Property States As EntitySet(Of State)
End Class

<TableMapping("tblStates")>
<HierarchyRoot(), KeyGenerator(KeyGeneratorKind.None)>
Public Class State
    Inherits Entity

    <Field(), Key()>
    Property ID As Integer

    <Field(), FieldMapping("geoLocationID")>
    Property GeoLocation As GeoLocation

    <Field(Nullable:=False), FieldMapping("countryID"), Association("States")>
    Property Country As Country

    <Field(), Association("State")>
    Property Cities As EntitySet(Of City)
End Class

<TableMapping("tblCities")>
<HierarchyRoot(), KeyGenerator(KeyGeneratorKind.None)>
Public Class City
    Inherits Entity

    <Field(), Key()>
    Property ID As Integer

    <Field(Nullable:=False), FieldMapping("geoLocationID")>
    Property GeoLocation As GeoLocation

    <Field(Nullable:=False), FieldMapping("stateID"), Association("Cities")>
    Property State As State
End Class

<TableMapping("tblZipCodes")>
<HierarchyRoot(), KeyGenerator(KeyGeneratorKind.None)>
Public Class ZipCode
    Inherits Entity

    <Field(), Key()>
    Property ID As Integer

    <Field(Nullable:=True), FieldMapping("geoLocationID")>
    Property GeoLocation As GeoLocation

    <Field(), Association("ZipCodes")>
    Property AreaCodes As EntitySet(Of AreaCode)
End Class

<TableMapping("tblAreaCodes")>
<HierarchyRoot(), KeyGenerator(KeyGeneratorKind.None)>
Public Class AreaCode
    Inherits Entity

    <Field(), Key()>
    Property ID As Integer

    <Field(Nullable:=False), FieldMapping("geoLocationID")>
    Property GeoLocation As GeoLocation

    <Field(), Association("AreaCodes")>
    Property ZipCodes As EntitySet(Of ZipCode)
End Class

I have tried to post a simplified example of my problem. If the full code is needed to diagnose the issue then I can make it available in a zip archive. If there are any other questions I can answer or information I can provide about what I am trying to do or how I am trying to do it, please let me know. Thank you very much for your time and assistance.