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I am implementing HotChocolate as part of my ASP.NET API. I'm trying to add subscriptions to the chat portion on my app, however, the documentation on the HotChocolate site is not implemented yet. From what I can tell from other sites/frameworks, I can use the C# IObservable<Chat> as the return type for the subscription method.
Can anyone give me an example of a query method or point me towards another resource?
public async Task<IObservable<Message>> GetMessages(Guid chatId) {
var messages = ..Get chats;
return messages;
}
However, how does this work from a query standpoint? How do we trigger an event to update this?
Thanks.
300
GraphQL uses Event-based approach to implement its subscription operation. The client subscribes for some particular events to the server. The server informs the client whenever these events trigger.
Like queries, subscriptions enable you to fetch data. Unlike queries, subscriptions are long-lasting operations that can change their result over time. They can maintain an active connection to your GraphQL server (most commonly via WebSocket), enabling the server to push updates to the subscription's result.
Subscriptions are a GraphQL feature allowing the server to send data to its clients when a specific event happens. Subscriptions are usually implemented with WebSockets, where the server holds a steady connection to the client.
GraphQL subscriptions enable publishing updates to data in real time to subscribed clients. They are invoked in response to a mutation or change in data. In other words, when data is modified via a GraphQL mutation operation, subscribed clients are automatically notified accordingly.
Since the original documentation link became obsolete I am posting this new link that refers to our workshop project.
Chapter 7 shows how to do subscriptions in two variants. https://github.com/ChilliCream/graphql-workshop/blob/master/docs/7-subscriptions.md
I hope that helps.
194
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