DependencyWalker.DiscoverDependencies fails with System.ArgumentException: Item has already been added.

We hit this when we had a few old stored procedures referring to the same dropped table with different casing for database name. I see commented out code at https://github.com/microsoft/sqlmanagementobjects/blob/main/src/Microsoft/SqlServer/Management/Smo/DependencyTree.cs#L198 that might have fixed this issue, not sure why it's been commented out though.

Microsoft.SqlServer.Management.Smo.FailedOperationException: Discover dependencies failed. 
 ---> System.ArgumentException: Item has already been added. Key in dictionary: 'Server[@Name='SERVER']/Database[@Name='database']/UnresolvedEntity[@Name='nonexisting_table' and @Schema='dbo']'  Key being added: 'Server[@Name='SERVER']/Database[@Name='DATABASE']/UnresolvedEntity[@Name='nonexisting_table' and @Schema='dbo']'
   at Microsoft.SqlServer.Management.Smo.DependencyTree..ctor(Urn[] urns, DependencyChainCollection dependencies, Boolean fParents, Server server)
   at Microsoft.SqlServer.Management.Smo.DependencyWalker.DiscoverDependencies(Urn[] urns, Boolean parents)

src/Microsoft/SqlServer/Management/Smo/DependencyTree.cs の 198 行目付近から始め、未解決のエンティティがどのようにキー付けされるかについて DependencyWalker.DiscoverDependencies を追跡してください。データベース名の大文字と小文字だけが異なる参照で失敗を再現し、その後、コメントアウトされたロジックを評価してください。大文字と小文字が異なる同等の未解決参照を使用しても、依存関係の検出で例外がスローされなくなれば完了です。