ASP.Net access enviroment variables in singleton class

Question

i need to access my enviroment variables from a singleton class.

I only found soulutions where the WebBuilder injects the configuration through the constructor or methods to a PageModel.

Singleton Class

public class GraphQLAPI
{
    public static GraphQLAPI Instance { 
        get 
        {
            if (_instance == null)
                _instance = new GraphQLAPI();

            return _instance;
        } 
    }
    private static GraphQLAPI _instance;
    private GraphQLAPI() 
    {
        
        _qlClient = new GraphQLHttpClient("XXX", new SystemTextJsonSerializer());
        _qlClient.HttpClient.DefaultRequestHeaders.Add("Authorization", "XXX");
    }
    [...]
}

Is it even possible? If not, is there another way to pass the value to my client?

Answer 1

I just created 2 static fields in the GraphQLAPI.cs which will be set in the Startup.cs

GraphQLAPI.cs

public class GraphQLAPI
{
    public static string GraphQLHostUrl { get; set; }
    public static string GraphQLAuthorization { get; set; }

    [...]
    private GraphQLAPI() 
    {
        
        _qlClient = new GraphQLHttpClient(GraphQLHostUrl, new SystemTextJsonSerializer());
        _qlClient.HttpClient.DefaultRequestHeaders.Add("Authorization", GraphQLAuthorization);
    
    }
    [...]
}

Startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
        GraphQLAPI.GraphQLHostUrl = configuration.GetValue<string>("GraphQlUrl");
        GraphQLAPI.GraphQLAuthorization = configuration.GetValue<string>("ApiAuthorization");
    }
    [...]
}