dotnet-sdk/samples/AspNetCore/ControllerSample

ASP.NET Core Controller Sample

This sample shows using Dapr with ASP.NET Core routing. 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.

Running the Sample

To run the sample locally run this comment in this directory:

dapr run --app-id routing --app-port 5000 dotnet run

The application will listen on port 5000 for HTTP.

Examples

Deposit Money

On Linux, MacOS:

curl -X POST http://127.0.0.1:5000/deposit \
       -H 'Content-Type: application/json' \
       -d '{ "id": "17", "amount": 12 }'

On Windows:

curl -X POST http://127.0.0.1:5000/deposit -H "Content-Type: application/json" -d "{ \"id\": \"17\", \"amount\": 12 }"

Output:

 {"id":"17","balance":12}

---

Withdraw Money On Linux, MacOS:

curl -X POST http://127.0.0.1:5000/withdraw \
       -H 'Content-Type: application/json' \
       -d '{ "id": "17", "amount": 10 }'

On Windows:

curl -X POST http://127.0.0.1:5000/withdraw -H "Content-Type: application/json" -d "{ \"id\": \"17\", \"amount\": 10 }"

Outpt:

{"id":"17","balance":2}

---

Get Balance

curl http://127.0.0.1:5000/17

Output:

{"id":"17","balance":2}

---

Withdraw Money (pubsub)

Publish events using Dapr cli:

On Linux, MacOS:

dapr publish -t withdraw -p '{"id": "17", "amount": 15 }'

On Windows:

dapr publish -t withdraw -p "{\"id\": \"17\", \"amount\": 15 }"

---

Deposit Money (pubsub) Publish events using Dapr cli: On Linux, MacOS:

dapr publish -t deposit -p '{"id": "17", "amount": 15 }'

On Windows:

dapr publish -t deposit -p "{\"id\": \"17\", \"amount\": 15 }"

---

Code Samples

All of the interesting code in this sample is in Startup.cs and Controllers/SampleController.cs

 public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers().AddDapr();

    ...
}

AddDapr() registers the Dapr integration with controllers. This also registers the StateClient service with the dependency injection container. This service can be used to interact with the Dapr state-store.

---

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.

---

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.

---

[Topic("deposit")]
[HttpPost("deposit")]
public async Task<ActionResult<Account>> Deposit(...)
{
    ...
}

[Topic(...)] associates a pub-sub topic with this endpoint.

---

[HttpGet("{account}")]
public ActionResult<Account> Get(StateEntry<Account> 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:

[HttpGet("{account}")]
public ActionResult<Account> Get([FromState] Account account)
{
    ...
}

[HttpGet("{id}")]
public ActionResult<Account> 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.

---

[Topic("deposit")]
[HttpPost("deposit")]
public async Task<ActionResult<Account>> Deposit(Transaction transaction, [FromServices] StateClient stateClient)
{
    var state = await stateClient.GetStateEntryAsync<Account>(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<>.