# ASP.NET Core Controller example This sample shows using Dapr with ASP.NET Core controllers. This application is a simple and not-so-secure banking application. The application uses the Dapr state-store for its data storage. It exposes the following endpoints over HTTP: - GET `/{account}`: Get the balance for the account specified by `id` - POST `/deposit`: Accepts a JSON payload to deposit money to an account - POST `/withdraw`: Accepts a JSON payload to withdraw money from an account The application also registers for pub/sub with the `deposit` and `withdraw` topics. ## Prerequisitess - [.NET Core 3.1 or .NET 5+](https://dotnet.microsoft.com/download) installed - [Dapr CLI](https://docs.dapr.io/getting-started/install-dapr-cli/) - [Initialized Dapr environment](https://docs.dapr.io/getting-started/install-dapr-selfhost/) - [Dapr .NET SDK](https://docs.dapr.io/developing-applications/sdks/dotnet/) ## Running the example To run the sample locally run this command in this project root directory: ```sh dapr run --app-id controller --app-port 5000 -- dotnet run ``` The application will listen on port 5000 for HTTP. ### Examples **Deposit Money** On Linux, MacOS: ```sh curl -X POST http://127.0.0.1:5000/deposit \ -H 'Content-Type: application/json' \ -d '{ "id": "17", "amount": 12 }' ``` On Windows: ```sh curl -X POST http://127.0.0.1:5000/deposit -H "Content-Type: application/json" -d "{ \"id\": \"17\", \"amount\": 12 }" ``` Or, we can also do this using the Visual Studio Code [Rest Client Plugin](https://marketplace.visualstudio.com/items?itemName=humao.rest-client) [sample.http](sample.http) ```http POST http://127.0.0.1:5000/deposit Content-Type: application/json { "id": "17", "amount": 12 } ``` Output: ```txt {"id":"17","balance":12} ``` --- **Withdraw Money** On Linux, MacOS: ```sh curl -X POST http://127.0.0.1:5000/withdraw \ -H 'Content-Type: application/json' \ -d '{ "id": "17", "amount": 10 }' ``` On Windows: ```sh curl -X POST http://127.0.0.1:5000/withdraw -H "Content-Type: application/json" -d "{ \"id\": \"17\", \"amount\": 10 }" ``` or using the Visual Studio Code [Rest Client Plugin](https://marketplace.visualstudio.com/items?itemName=humao.rest-client) [sample.http](sample.http) ```http POST http://127.0.0.1:5000/withdraw Content-Type: application/json { "id": "17", "amount": 5 } ``` Output: ```txt {"id":"17","balance":2} ``` --- **Get Balance** ```sh curl http://127.0.0.1:5000/17 ``` or using the Visual Studio Code [Rest Client Plugin](https://marketplace.visualstudio.com/items?itemName=humao.rest-client) [sample.http](sample.http) ```http GET http://127.0.0.1:5000/17 ``` Output: ```txt ```txt {"id":"17","balance":2} ``` --- **Withdraw Money (pubsub)** Publish events using Dapr cli: On Linux, MacOS: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t withdraw -d '{"id": "17", "amount": 15 }' ``` On Windows: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t withdraw -d "{\"id\": \"17\", \"amount\": 15 }" ``` --- **Deposit Money (pubsub)** Publish events using Dapr cli: On Linux, MacOS: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d '{"id": "17", "amount": 15 }' ``` On Windows: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d "{\"id\": \"17\", \"amount\": 15 }" ``` --- **Dead Letter Topic example (pubsub)** Publish an event using the Dapr cli with an incorrect input, i.e. negative amount: Deposit: On Linux, MacOS: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d '{"id": "17", "amount": -15 }' ``` On Windows: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d "{\"id\": \"17\", \"amount\": -15 }" ``` Withdraw: On Linux, MacOS: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t withdraw -d '{"id": "17", "amount": -15 }' ``` On Windows: ```sh dapr publish --pubsub pubsub --publish-app-id controller -t withdraw -d "{\"id\": \"17\", \"amount\": -15 }" ``` First a message is sent from a publisher on a `deposit` or `withdraw` topic. Dapr receives the message on behalf of a subscriber application, however the `deposit` or `withdraw` topic message fails to be delivered to the `/deposit` or `/withdraw` endpoint on the application, even after retries. As a result of the failure to deliver, the message is forwarded to the `amountDeadLetterTopic` topic which delivers this to the `/deadLetterTopicRoute` endpoint. --- ## Code Samples *All of the interesting code in this sample is in Startup.cs and Controllers/SampleController.cs* ```C# public void ConfigureServices(IServiceCollection services) { services.AddControllers().AddDapr(builder => builder.UseJsonSerializationOptions( new JsonSerializerOptions() { PropertyNamingPolicy = JsonNamingPolicy.CamelCase, PropertyNameCaseInsensitive = true, })); ... } ``` `AddDapr()` registers the Dapr integration with controllers. This also registers the `DaprClient` service with the dependency injection container (using the sepcified `DaprClientBuilder` for settings options). This service can be used to interact with the dapr runtime (e.g. invoke services, publish messages, interact with a state-store, ...). --- ```C# app.UseCloudEvents(); ``` `UseCloudEvents()` registers the Cloud Events middleware in the request processing pipeline. This middleware will unwrap requests with Content-Type `application/cloudevents+json` so that model binding can access the event payload in the request body directly. This is recommended when using pub/sub unless you have a need to process the event metadata yourself. --- ```C# app.UseEndpoints(endpoints => { endpoints.MapSubscribeHandler(); endpoints.MapControllers(); }); ``` `MapSubscribeHandler()` registers an endpoint that will be called by the Dapr runtime to register for pub/sub topics. This is is not needed unless using pub/sub. --- ```C# [Topic("pubsub", "deposit")] [HttpPost("deposit")] public async Task> Deposit(...) { ... } ``` `[Topic(...)]` associates a pub/sub named `pubsub` (this is the default configured by the Dapr CLI) pub/sub topic `deposit` with this endpoint. --- ```C# [HttpGet("{account}")] public ActionResult Get(StateEntry account) { if (account.Value is null) { return NotFound(); } return account.Value; } ``` Dapr's controller integration can automatically bind data from the state-store to an action parameter. Since the parameter's name is `account` the value of the account route-value will be used as the key. The data is stored in the state-store as JSON and will be deserialized as an object of type `Account`. This could alternatively be written as: ```C# [HttpGet("{account}")] public ActionResult Get([FromState] Account account) { ... } [HttpGet("{id}")] public ActionResult Get([FromState("id")] Account account) { ... } ``` Using `[FromState]` allows binding a data type directly without using `StateEntry<>`. `[FromState(...)]` can also be used to specify which route-value contains the state-store key. --- ```C# [Topic("pubsub", "deposit")] [HttpPost("deposit")] public async Task> Deposit(Transaction transaction, [FromServices] StateClient stateClient) { var state = await stateClient.GetStateEntryAsync(transaction.Id); state.Value.Balance += transaction.Amount; await state.SaveAsync(); return state.Value; } ``` The `StateClient` can be retrieved from the dependency injection container, and can be used to imperatively access the state-store. `state.SaveAsync()` can be used to save changes to a `StateEntry<>`.