GitBook: [master] 5 pages modified

docs/SUMMARY.md

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 ## Cronus Framework
 
+* [Concepts](cronus-framework/concepts/README.md)
+  * [DDD](cronus-framework/concepts/ddd.md)
+  * [CQRS](cronus-framework/concepts/cqrs.md)
 * [Domain Modeling](cronus-framework/domain-modeling/README.md)
   * [Aggregate](cronus-framework/domain-modeling/aggregate.md)
   * [Entity](cronus-framework/domain-modeling/entity.md)

docs/cronus-framework/concepts/README.md

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+# Concepts
+

docs/cronus-framework/concepts/cqrs.md

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+# CQRS
+

docs/cronus-framework/concepts/ddd.md

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+# DDD
+

docs/message-handlers/application-services.md

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 # Application Services
 
+ This is a handler where commands are received and delivered to the addressed AggregateRoot. We call these handlers _ApplicationService_. This is the _write side_ in CQRS.
+
+## Communication Guide Table
+
+| Triggered by | Description |
+| :--- | :--- |
+| Command | A command is used to dispatch domain model changes. It can either be accepted or rejected depending on the domain model invariants |
+
+## Best Practices
+
+{% hint style="success" %}
+**You can/should/must...**
+
+* an appservice **can** load an aggregate root from the event store
+* an appservice **can** save new aggregate root events to the event store
+* an appservice **can** establish calls to the ReadModel \(not common practice but sometimes needed\)
+* an appservice **can** establish calls to external services
+* you **can** do dependency orchestration
+* an appservice **must** be stateless
+* an appservice **must** update only one aggregate root. Yes, this means that you can create one aggregate and update another one but think twice
+{% endhint %}
+
+{% hint style="warning" %}
+**You should not...**
+
+* an appservice **should not** update more than one aggregate root in single command/handler
+* you **should not** place domain logic inside an application service
+* you **should not** use application service to send emails, push notifications etc. Use Port or Gateway instead
+* an appservice **should not** update the ReadModel
+{% endhint %}
+
+## Examples
+
+```csharp
+public class AccountAppService : AggregateRootApplicationService<Account>,
+    ICommandHandler<RegisterAccount>,
+    ICommandHandler<ActivateAccount>,
+    ICommandHandler<SuspendAccount>,
+    ICommandHandler<ResetAccountPassword>,
+    ICommandHandler<ChangeAccountEmail>,
+    ICommandHandler<ChangeAccountUsername>
+{
+    public void Handle(SuspendAccount message)
+    {
+        Update(message.Id, account => account.Suspend());
+    }
+
+    ...
+}
+```
+