How to consume GraphQL Subscriptions in C# using GraphQL.Client

2 min read 05-10-2024

How to consume GraphQL Subscriptions in C# using GraphQL.Client

Consuming GraphQL Subscriptions with GraphQL.Client in C#

Problem: You need to implement real-time data updates in your C# application by leveraging the power of GraphQL subscriptions.

Solution: This article will guide you through consuming GraphQL subscriptions in your C# application using the popular GraphQL.Client library.

Setting the Stage:

Let's imagine you're building an application that displays live stock prices. Using a GraphQL server, you have a subscription query that pushes updates whenever a stock price changes. You need a C# client to receive and process these real-time updates.

// Example GraphQL Subscription Query
subscription {
  stockPriceUpdates(symbol: "AAPL") {
    symbol
    price
  }
}

Code Walkthrough:

Install the GraphQL.Client Library:
```
Install-Package GraphQL.Client
```

Define the Subscription Request:

using GraphQL.Client.Http;
using GraphQL.Client.Serializer.Newtonsoft;

// Create a new GraphQL client instance
var graphQLClient = new GraphQLHttpClient("https://your-graphql-api.com/graphql", new NewtonsoftJsonSerializer());

// Define the subscription query
var subscriptionQuery = new GraphQLRequest
{
    Query = @"
        subscription {
            stockPriceUpdates(symbol: ""AAPL"") {
                symbol
                price
            }
        }
    "
};

// Create a subscription for the query
var subscription = graphQLClient.CreateSubscription(subscriptionQuery);

Subscribe to Events:

// Subscribe to the subscription's 'OnData' event
subscription.OnData += (sender, data) =>
{
    // Process the subscription data here
    Console.WriteLine({{content}}quot;Symbol: {data.stockPriceUpdates.symbol}, Price: {data.stockPriceUpdates.price}");
};

// Start the subscription
await subscription.StartAsync();

// Wait for a few seconds to receive data
await Task.Delay(5000);

Unsubscribe:

// Unsubscribe from the subscription
await subscription.DisposeAsync();

Breakdown and Insights:

GraphQLHttpClient: The GraphQLHttpClient class provides a convenient way to interact with your GraphQL server.
GraphQLRequest: This class represents your GraphQL query or mutation.
CreateSubscription: The CreateSubscription method allows you to register a subscription for your query.
OnData Event: The OnData event is triggered whenever new data is received from the subscription.
Data Processing: Within the OnData event handler, you can access and process the received data.
Asynchronous Operations: Remember that GraphQL subscriptions are asynchronous operations, so you need to use async and await keywords to manage the asynchronous data flow.

Key Considerations:

Connection Management: Consider the potential challenges of maintaining a persistent connection to your GraphQL server, especially if the network becomes unreliable.
Error Handling: Implement robust error handling to catch potential subscription errors and maintain the stability of your application.
Data Serialization: Ensure that the data received from the subscription is properly deserialized into your C# objects.

Conclusion:

By leveraging the GraphQL.Client library and understanding the principles of GraphQL subscriptions, you can easily integrate real-time data updates into your C# applications. This allows for dynamic and responsive user interfaces that stay up-to-date with the latest information.

Additional Resources:

GraphQL.Client Library: https://github.com/graphql-dotnet/graphql-client
GraphQL Documentation: https://graphql.org/

This article has provided you with a solid foundation for consuming GraphQL subscriptions in your C# applications. Remember to experiment with different scenarios and adapt the code to suit your specific needs.