This is an example of using the C# Octokit.GraphQL wrapper library to query if the logged in user is an active sponsor of 'warrenbuckley'

ActiveGithubSponsor.cs

using Octokit.GraphQL;
using Octokit.GraphQL.Model;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace Octokit
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var productInformation = new ProductHeaderValue("ExampleCode", "1.0");

            // Personal Access Token - needs a scope of 'read:user'
            var connection = new Connection(productInformation, "LOGGED_IN_GITHUB_USER_TOKEN");

            // A query to list out who you are actively sponsoring
            // With Octokit.GraphQL Nuget package
            var query = new Query()
                .Viewer
                .SponsorshipsAsSponsor()
                .AllPages()
                .Select(sponsoring => new
                {
                    User = sponsoring.Sponsorable
                            .Cast<User>()
                            .Select(x => new { 
                                x.Login,
                                x.Name,
                                x.Id
                            })
                            .Single()
                })
                .Compile();

            // Generates GraphQL query
            /*
            {
                viewer {
                    id
                    sponsorshipsAsSponsor(first: 100) {
                        pageInfo {
                            hasNextPage
                            endCursor
                        }
                        nodes {        
                            sponsorable {
                                __typename
                                ... on User {
                                    login
                                    name
                                    id
                                }
                            }
                        }
                    }
                }
            }
            */

            // Example JSON result from GraphQL call
            /*
            {
                "data": {
                    "viewer": {
                    "id": "MDQ6VXNlcjE3NDI2ODU=",
                    "sponsorshipsAsSponsor": {
                        "pageInfo": {
                        "hasNextPage": false,
                        "endCursor": "MQ"
                        },
                        "nodes": [
                        {
                            "sponsorable": {
                            "__typename": "User",
                            "login": "warrenbuckley",
                            "name": "Warren Buckley",
                            "id": "MDQ6VXNlcjEzODk4OTQ="
                            }
                        }
                        ]
                    }
                    }
                }
            }
            */
            var result = await connection.Run(query);
            
            
            // Sponsoring 'warrenbuckley' ?
            var activeSponsor = result.SingleOrDefault(x => x.User.Login.ToLowerInvariant() == "warrenbuckley");
            if(activeSponsor != null)
            {
                Console.WriteLine("Thanks for sponsoring Warren");
            }
        }
    }
}