RoutingSample

ASP.NET Core routing example

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 /{id}: 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.

Prerequisites

• .NET Core 3.1 or .NET 5+ installed
• Dapr CLI
• Initialized Dapr environment
• Dapr .NET SDK

Running the Sample

To run the sample locally run this command in this project root 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 }"

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:

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

---

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

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

On Windows:

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

On Windows:

dapr publish --pubsub pubsub --publish-app-id routing -t deposit -d "{\"id\": \"17\", \"amount\": 15 }"

---

Code Samples

All of the interesting code in this sample is in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
   services.AddDaprClient(builder =>
       builder.UseJsonSerializationOptions(
           new JsonSerializerOptions()
           {
               PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
               PropertyNameCaseInsensitive = true,
           }));

   ...
}

AddDaprClient() 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 application code 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.MapGet("{id}", Balance);
    endpoints.MapPost("deposit", Deposit).WithTopic(PubsubName, "deposit");
    endpoints.MapPost("withdraw", Withdraw).WithTopic(PubsubName, "withdraw");
});

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.

MapGet(...) and MapPost(...) are provided by ASP.NET Core routing - these are used to setup endpoints to handle HTTP requests.

WithTopic(...) associates an endpoint with a pub/sub topic.

---

async Task Balance(HttpContext context)
{
    var client = context.RequestServices.GetRequiredService<StateClient>();

    var id = (string)context.Request.RouteValues["id"];
    var account = await client.GetStateAsync<Account>(id);
    if (account == null)
    {
        context.Response.StatusCode = 404;
        return;
    }

    context.Response.ContentType = "application/json";
    await JsonSerializer.SerializeAsync(context.Response.Body, account, serializerOptions);
}

Here GetRequiredService<StateClient>() is used to retrieve the StateClient from the service provider.

client.GetStateAsync<Account>(id) is used to retrieve an Account object from that state-store using the key in the variable id. The Account object stored in the state-store as JSON. If no entry is found for the specified key, then null will be returned.

---

await client.SaveStateAsync(transaction.Id, account);

SaveStateAsync(...) is used to save data to the state-store.