Tanka GraphQL .NET Client library

This library provides easy to use cross-platform client API for Tanka GraphQL execution library based server using ASP.NET Core SignalR .NET Clients HubConnection.

Features

• Execute queries, mutations and subscriptions using SignalR HubConnection
• Supports GraphQL validation and tracing
• Leverage power of SignalR communication techniques (WebSockets, Server-Sent Events, Long Polling)

Gettings started

Install

Current release is available on Nuget gallery.

Install-Package Tanka.GraphQL.Net.Client -Version 0.3.2

To access latest (pre-release) builds, you can connect to a following feed:

https://pkgs.dev.azure.com/anttikajanus/_packaging/tanka-graphql-net-client-packages/nuget/v3/index.json

See how to add custom nuget feeds in Visual Studio from here

Short API summary

Add usings

using Tanka.GraphQL;

Defining models

You can define your DTOs as POCOs. In these examples, I'm using separate models for input and output messages.

public class Message
{
    public int Id { get; set; }
    public string Content { get; set; }
}

public class InputMessage
{
    public string Content { get; set; }
}

Connect to the server endpoint

Create SignalR HubConnection normally. Read more how to connect to a hub

Read more about the server implementation from Tanka GraphQL documentation

var connection = new HubConnectionBuilder()
                    .WithUrl("http://localhost:5000/hubs/graphql")
                    .Build();
await connection.StartAsync();

Queries and mutations

In GraphQL both queries and mutations are defined as queries so they are handled the same way in the API.

Query

var channelId = 1;

var channelMessageGQL = @"query Messages($channelId: Int!) {
                messages(channelId: $channelId) {
                  id
                  content
                }
            }";

var queryRequest = new QueryRequest()
{
    Query = channelMessageGQL,
    Variables = new Dictionary<string, object>()
        {
            { "channelId", channelId }
        }
};

var result = await connection.QueryAsync(queryRequest);
var data = result.GetDataFieldAs<List<Message>>();

Mutation

var postMessageMutationGQL = @"mutation PostMessage($channelId: Int!, $message: InputMessage) {
               postMessage(channelId: $channelId, message: $message) {
                 id
                 content
               }
            }";

var queryRequest = new QueryRequest()
{
    Query = postMessageMutationGQL,
    Variables = new Dictionary<string, object>()
        {
            { "channelId", channelId },
            { "message", new InputMessage() { Content = message } }
        }
};

var result = await connection.QueryAsync(queryRequest);
var data = result.GetDataFieldAs<Messages>();

Subscription

API provides support for subscriptions as streams using IObservable<ExecutionResult>. You can subscribe to the stream using Subscribe method.

 var channelSubsribtionGQL = @"subscription MessageAdded($channelId: Int!) {
                messageAdded(channelId: $channelId) {
                  id
                  content
                }
            }";

var queryRequest = new QueryRequest()
{
    Query = channelSubsribtionGQL,
    Variables = new Dictionary<string, object>()
        {
            { "channelId", channelId}
        }
};

var subscriptionSource = new CancellationTokenSource();
var serverSubscription = await connection.SubscribeAsync(request, subscriptionSource);
serverSubscription.Subscribe(
                // On new message added
                result =>
                {
                    var message = result.GetDataFieldAs<Message>();
                    // Handle new message added
                },
                // On error corrured
                error =>
                {
                    //Handle error
                },
                // On completed
                () =>
                {
                   //No more messages coming
                });
                
// Cancelling the subscription                
subscriptionSource.Cancel();