> For the complete documentation index, see [llms.txt](https://docs.umbraco.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.umbraco.com/umbraco-cms/17.latest/develop-with-umbraco/application-code.md). # Application Code Build custom backend logic, set up routing and controllers, use dependency injection, and search content with Examine. This section covers C# development within Umbraco. Topics include custom controllers, routing, dependency injection, subscribing to notifications, Examine search, and common application code pitfalls.


Backend and Custom Logic	Build custom controllers, configure routing, use dependency injection, subscribe to notifications, and access Umbraco services.	Backend & Custom Logic
Searching with Examine	Index and search Umbraco content and media using Examine, a Lucene-based search library with Umbraco-specific APIs.	Searching with Examine
Common Pitfalls	Learn about common mistakes in Umbraco application code and how to avoid them.	Common Pitfalls & Anti-Patterns

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