dotnet-sdk/examples/AspNetCore/ControllerSample

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+ installed
• Dapr CLI
• Initialized Dapr environment
• Dapr .NET SDK

Running the example

To run the sample locally run this command in this project root directory:

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:

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 }"

Or, we can also do this using the Visual Studio Code Rest Client Plugin

sample.http

POST http://127.0.0.1:5000/deposit
Content-Type: application/json

{ "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 }"

or using the Visual Studio Code Rest Client Plugin

sample.http

POST http://127.0.0.1:5000/withdraw
Content-Type: application/json

{ "id": "17", "amount": 5 }

Output:

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

---

Get Balance

curl http://127.0.0.1:5000/17

or using the Visual Studio Code Rest Client Plugin

sample.http

GET http://127.0.0.1:5000/17

Output:

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

---

Withdraw Money (pubsub)

Publish events using Dapr cli:

On Linux, MacOS:

dapr publish --pubsub pubsub --publish-app-id controller -t withdraw -d '{"id": "17", "amount": 15 }'

On Windows:

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:

dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d '{"id": "17", "amount": 15 }'

On Windows:

dapr publish --pubsub pubsub --publish-app-id controller -t deposit -d "{\"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(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, ...).

---

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

[Topic(...)] associates a pub/sub named pubsub (this is the default configured by the Dapr CLI) pub/sub topic deposit 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("pubsub", "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<>.