[ApiController]
public class SomeController : ControllerBase
{public class TwitterTweet{[JsonPropertyName("id_str")]public string ID {get; set; }[JsonPropertyName("text")]public string Text {get; set; }}[HttpPost("/tweet")]public ActionResult Post(TwitterTweet tweet){// Handle tweetConsole.WriteLine("Tweet received: {0}: {1}", tweet.ID, tweet.Text);// ...// Acknowledge messagereturn Ok();}
}

If the operation should error, you would return the appropriate 400 or 500 level HTTP status code. For bindings that feature at-least-once-delivery guarantees, the Dapr sidecar will retry the trigger. Check out [Dapr documentation for resource bindings][1] to see whether they offer at-least-once or exactly-once delivery guarantees.

如果操作错误，则会返回相应的400或500级别的 HTTP 状态码。对于 至少传递一次 的绑定保证，Dapr 边车将重试触发。查看 [有关资源绑定的 Dapr 文档] [1]，来查看它们是否提供了 " 至少一次 " 或 "一次性交付 保证"。

Output bindings

输出绑定

Dapr also includes output binding capabilities. They enable your service to trigger an event that invokes an external resource. Again, you start by configuring a binding configuration YAML file that describes the output binding. Once in place, you trigger an event that invokes the bindings API on the Dapr sidecar of your application. Figure 8-3 shows the flow of an output binding:

Dapr 还包括 输出绑定 功能。它们使服务能够触发调用外部资源的事件。同样，您首先配置描述输出绑定的绑定配置 YAML 文件。一旦准备好，可以触发一个事件，该事件在应用程序的 Dapr 边车上调用绑定 API。图8-3 显示了输出绑定的工作流：

Figure 8-3. Dapr output binding flow.

图 8-3。Dapr 输出绑定流。

As an example, you can invoke an output binding by invoking the Dapr API using curl:

例如，你可以通过使用curl调用 Dapr API 来调用输出绑定：

curl -X POST http://localhost:3500/v1.0/bindings/sms \-H "Content-Type: application/json" \-d '{"data": "Welcome to this awesome service","metadata": {"toNumber": "555-3277"},"operation": "create"}'

Note that the HTTP port is the same as used by the Dapr sidecar (in this case, the default Dapr HTTP port 3500).

请注意，HTTP 端口与 Dapr 边车使用相同的端口 (在本例中为默认 Dapr HTTP 端口3500) 。

The structure of the payload (that is, message sent) will vary per binding. In the example above, the payload contains a data element with a message. Bindings to other types of external resources can be different, especially for the metadata that is sent. Each payload must also contain an operation field, that defines the operation the binding will execute. The above example specifies a create operation that creates the SMS message. Common operations include:

负载 (发送的消息) 的结构将因绑定而异。在上面的示例中，负载包含 data 元素。与其他类型的外部资源的绑定可能不同，尤其是元数据metadata 。每个负载还必须包含一个 operation 字段，该字段定义绑定将执行的操作。上面的示例指定了 create 操作以创建 SMS 消息。常见操作包括：

It's up to the author of the binding which operations the binding supports. The documentation for each binding describes the available operations and how to invoke them.

取决于绑定支持的操作。每个绑定的文档描述了可用的操作以及怎样调用。

Using the Dapr .NET SDK

使用 Dapr .NET SDK

The Dapr .NET SDK provides language-specific support for .NET Core developers. In the following example, the call to the HttpClient.PostAsync() is replaced with the DaprClient.InvokeBindingAsync() method. This specialized method simplifies invoking a configured output binding:

Dapr .NET SDK 为 .NET Core 开发人员提供特定于语言的支持。在下面的示例中，对HttpClient.PostAsync()的调用被替换为对DaprClient.InvokeBindingAsync() 方法的调用。此专用方法简化了调用已配置的输出绑定：

private async Task SendSMSAsync([FromServices] DaprClient daprClient)
{var message = "Welcome to this awesome service";var metadata = new Dictionary<string, string>{{ "toNumber", "555-3277" }};await daprClient.InvokeBindingAsync("sms", "create", message, metadata);
}

The method expects the metadata and message values.

此方法需要 metadata 和 message 值。

When used to invoke a binding, the DaprClient uses gRPC to call the Dapr API on the Dapr sidecar.

当用于调用绑定时，将 DaprClient 使用 gRPC 来调用 Dapr 边车上的 DAPR API。

Binding components

绑定组件

Under the hood, resource bindings are implemented with Dapr binding components. They're contributed by the community and written in Go. If you need to integrate with an external resource for which no Dapr binding exists yet, you can create it yourself. Check out the Dapr components-contrib repo to see how you can contribute a binding.

在后台，资源绑定是通过 Dapr 绑定组件实现的。它们由社区提供，使用Go开发。如果需要与还没有 Dapr 绑定的外部资源集成，可以自行创建。查看 Dapr 组件-contrib 存储库，了解如何参与绑定。

Note

Dapr and all of its components are written in the Golang (Go) language. Go is considered a modern, cloud-native programming platform.

备注

Dapr 及其所有组件都是以 Go 语言编写的。Go是现代的云本地编程平台。

You configure bindings using a YAML configuration file. Here's an example configuration for the Twitter binding:

使用 YAML 配置文件配置绑定。下面是用于 Twitter 绑定的示例配置：

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:name: twitter-mentionnamespace: default
spec:type: bindings.twitterversion: v1metadata:- name: consumerKeyvalue: "****" # twitter api consumer key, required- name: consumerSecretvalue: "****" # twitter api consumer secret, required- name: accessTokenvalue: "****" # twitter api access token, required- name: accessSecretvalue: "****" # twitter api access secret, required- name: queryvalue: "dapr" # your search query, required

Each binding configuration contains a general metadata element with a name and namespace field. Dapr will determine the endpoint to invoke your service based upon the configured name field. In the above example, Dapr will invoke the method annotated with /twitter-mention in your service when an event occurs.

每个绑定配置都包含一个包含 metadata 元素和name、namespace 字段。Dapr 将根据配置的name 字段确定要调用服务的终结点。在上面的示例中，Dapr 将在事件发生时调用在服务中（使用 /twitter-mention 批注）的方法。

In the spec element, you specify the type of the binding along with binding specific metadata. The example specifies credentials for accessing a Twitter account using its API. The metadata can differ between input and output bindings. For example, to use Twitter as an input binding, you need to specify the text to search for in tweets using the query field. Every time a matching tweet is sent, the Dapr sidecar will invoke the /twitter-mention endpoint on the service. It will also deliver the contents of the tweet.

在 spec 元素中，指定绑定的 type 和绑定特定的 metadata 。该示例指定了用于访问 Twitter 帐户的凭据，用于将来访问推特的api。输入绑定和输出绑定的元数据可以不同。例如，若要使用 Twitter 作为输入绑定，需要使用query 字段指定要在推文中搜索的文本。每次发送匹配的推文时，Dapr 边车将调用服务上的 /twitter-mention 终结点。它还将传递推文的内容。

A binding can be configured for input, output, or both. Interestingly, the binding doesn't explicitly specify input or output configuration. Instead, the direction is inferred by the usage of the binding along with configuration values.

可以将绑定配置为用于输入和/或输出。有趣的是，绑定未显式指定输入或输出配置。相反，通过使用绑定以及配置值进行推断方向。

The [Dapr documentation for resource bindings][1] provides a complete list of the available bindings and their specific configuration settings.

[资源绑定的 Dapr 文档] [1] 提供了可用绑定的完整列表及其特定的配置设置。

Cron binding

Cron 绑定

Pay close attention to Dapr's Cron binding. It doesn't subscribe to events from an external system. Instead, this binding uses a configurable interval schedule to trigger your application. The binding provides a simple way to implement a background worker to wake up and do some work at a regular interval, without the need to implement an endless loop with a configurable delay. Here's an example of a Cron binding configuration:

请密切注意 Dapr 的 Cron 绑定。它不订阅外部系统中的事件。相反，此绑定使用可配置的间隔计划来触发你的应用程序。绑定提供了一种简单的途径来实现后台工作线程唤醒，并定期执行一些工作，而无需实现具有可配置延迟的无限循环。下面是 Cron 绑定配置的示例：

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:name: checkOrderBacklognamespace: default
spec:type: bindings.cronversion: v1metadata:- name: schedulevalue: "@every 30m"

In this example, Dapr triggers a service by invoking the /checkOrderBacklog endpoint every 30 minutes. There are several patterns available for specifying the schedule value. For more information, see the Cron binding documentation.

在此示例中，Dapr 通过每隔30分钟调用 /checkOrderBacklog 终结点来触发服务。有多种可用于指定 schedule 值的模式。有关详细信息，请参阅 Cron 绑定文档。

Reference application: eShopOnDapr

参考应用程序：eShopOnDapr

The accompanying eShopOnDapr reference application implements an output binding example. It triggers the Dapr SendGrid binding to send a user an email when a new order is placed. You can find this binding in the eshop-email.yaml file in the components folder:

随附的 eShopOnDapr 参考应用程序实现了输出绑定示例。它触发 Dapr SendGrid 绑定，以便在有新订单时向用户发送电子邮件。可以在 components 文件夹的 eshop-email.yaml 文件中找到此绑定：

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:name: sendmailnamespace: eshop
spec:type: bindings.twilio.sendgridversion: v1metadata:- name: apiKeysecretKeyRef:name: sendGridAPIKey
auth:secretStore: eshop-secretstore

This configuration uses the Twilio SendGrid binding component. Note how the API key for connecting to the service consumes a Dapr secret reference. This approach keeps secrets outside of the configuration file. Read the secrets building block chapter to learn more about Dapr secrets.

此配置使用 Twilio SendGrid 绑定组件。请注意，用于连接到服务的 API 密钥怎样使用 Dapr 机密引用。此方法在配置文件之外保存机密。请参阅机密构建块章节，详细了解 Dapr 机密。

The binding configuration specifies a binding component that can be invoked using the /sendmail endpoint on the Dapr sidecar. Here's a code snippet in which an email is sent whenever an order is started:

绑定配置指定一个绑定组件，该组件可使用Dapr 边车上的 /sendmail 终结点进行调用。以下代码片段将在每次有新订单时发送电子邮件：

public Task Handle(OrderStartedDomainEvent notification, CancellationToken cancellationToken)
{var string message = CreateEmailBody(notification);var metadata = new Dictionary<string, string>{{"emailFrom", "eShopOn@dapr.io"},{"emailTo", notification.UserName},{"subject", $"Your eShopOnDapr order #{notification.Order.Id}"}};return _daprClient.InvokeBindingAsync("sendmail", "create", message, metadata, cancellationToken);
}

As you can see in this example, message contains the message body. The CreateEmailBody method simply formats a string with the body text. The metadata specifies the email sender, recipient, and the subject for the email message. If these values are static, they can also be included in the metadata fields in the configuration file. The name of the binding to invoke is sendmail and the operation is create.

如本示例中所示， message 包含消息正文。 CreateEmailBody方法只是将字符串转换为正文文本。 metadata 指定电子邮件发件人、收件人和电子邮件的主题。如果这些值是静态的，则也可以将它们包含在配置文件的元数据字段中。要调用的绑定的名称为 sendmail ，并且操作为 create 。