Cosmos: Adding an un-owned related entity

[elliotritchie]

Adding an un-owned related entity causes an exception to be thrown when SaveChanges is called:

using (var db = new BloggingContext())
{
    var blog = new Blog { Url = "http://blogs.msdn.com/adonet" };
    db.Add(blog);
    db.SaveChanges();
    blog.Posts.Add(new Post { Title = "Hello World", Content = "I wrote an app using EF Core!" });
    db.SaveChanges();
}

Microsoft.Azure.Cosmos.CosmosException : Response status code does not indicate success: NotFound (404); Substatus: 0; ActivityId: d90d9317-51d4-4e7e-8fb1-845cf6ef3ba8; Reason: (
Errors : [
  "Resource Not Found. Learn more: https://aka.ms/cosmosdb-tsg-not-found"
]

I'm using these workarounds for now:

using (var db = new BloggingContext())
{
    var blog = new Blog { Url = "http://blogs.msdn.com/adonet" };
    blog.Posts.Add(new Post { Title = "Hello World", Content = "I wrote an app using EF Core!" });
    db.Add(blog);
    db.SaveChanges();
}

using (var db = new BloggingContext())
{
    var blog = new Blog { Url = "http://blogs.msdn.com/adonet" };
    db.Add(blog);
    db.SaveChanges();
    var post = new Post { Title = "Hello World", Content = "I wrote an app using EF Core!" };
    blog.Posts.Add(post);
    db.Posts.Add(post);
    db.SaveChanges();
}

EF Core version: 6.0.0-preview.5.21301.9
Database provider: Microsoft.EntityFrameworkCore.Cosmos
Target framework: .NET 5.0

[smitpatel]

ChangeTracker marks Post entity as modified so we ends up issue ReplaceItem command which fails. Not sure why Post is not added rather than modified.