<p>Quick question: Would it be a good or a bad idea to implement my domain-driven design style repositories as singletons? Why?</p>

<p>Or should I maybe use a dependency injector container to manage my repositories and decide if they are singletons or not?</p>

<p>I'm still reading <em>DDD Quickly</em>, and would like to see some good repository examples.</p>

Use your dependency injection container to decide how and where repositories are created.
By using
```
```
UserRepository.Instance.Find(userId);
```
```
you're creating a barrier to testing.
If your repositories are passed into services using Constructor Injection, then you can also easily replace them with mocks.