Get Crypto Assets from GraphQL Backend

Now that we've created a UI that can display our Crypto assets, let's write the logic to retrieve the data from our GraphQL Backend.

1. GetAssestsQuery.graphql

Let's first see how StrawberryShake automatically generates C# code based on our *.graphql files

1. In Visual Studio, open Services/GraphQL/Operations/GetAssestsQuery.graphql

2. Here's a breakdown of how Strawberry Shake turns this GraphQL query into C# code:

   GetAssestsQuery.graphql	Strawberry Shake
   query GetAssestsQuery($after: String)	Generates a Method, GetAssestsQuery.ExecuteAsync(string? after, CancellationToken token)
   assets	Generates an interface, interface IGetAssestsQuery_Assets
   nodes	Generates an interface, interface IGetAssestsQuery_Assets_Nodes
   price	Generates an interface, interface IGetAssestsQuery_Assets_Nodes_Price
   pageInfo	Generates an interface, interface IGetAssestsQuery_Assets_PageInfo

2. Add GetAssestsQuery Logic

1. In Visual Studio, open Services/GraphQL/CryptoGraphQLService.cs

2. In CryptoGraphQLService, update the GetAssestsQuery method with the following code:

   public async IAsyncEnumerable<IGetAssestsQuery_Assets_Nodes?> GetAssestsQuery([EnumeratorCancellation] CancellationToken token)
   {
       string? endCursor = null;
       IGetAssestsQueryResult? queryResult;
   
       do
       {
           var result = await _cryptoClient.GetAssestsQuery.ExecuteAsync(endCursor, token).ConfigureAwait(false); // Executes the GetAssestsQuery
           result.EnsureNoErrors(); // Throws a GraphQLClientException if the GraphQL Server returns an error
   
           queryResult = result.Data;
   
           if (queryResult?.Assets?.Nodes is not null)
           {
               foreach (var node in queryResult.Assets.Nodes)
               {
                   yield return node;
               }
           }
   
           endCursor = queryResult?.Assets?.PageInfo?.EndCursor; // Upates the endCursor (used for pagination)
   
       } while (queryResult?.Assets?.PageInfo?.HasNextPage is true); // Continues pagination until HasNextPage is false
   }

3. Run the App + Verify Data

1. In Visual Studio, build + deploy the Android app to the Android Emulator
2. In the Android Emulator, on the Dashbaord page, verify data from the GraphQL Backend is now displayed

3. On the Dashboard page, on the top cyrpto ticker, scroll right-to-left until the data for BTC is displayed
4. On the Dashboard page, note the price of BTC
5. In the Android Emulator, navigate to the Screener page
6. On the Screener page, verify the price of BTC is incorect because the same data we hard-coded is displayed