c# asp.net core health check that looks at the result of the query to determine healthy or not

SqlExamineResultHealthCheck.cs

using System;
using System.Data.Common;
using System.Data.SqlClient;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Diagnostics.HealthChecks;

namespace YOUR_NAMESPACE_HERE
{    
    public class SqlExamineResultHealthCheck : IHealthCheck
    {
        private const string _defaultTestQuery = "Select 1";

        public string ConnectionString { get; }

        public string TestQuery { get; }

        public SqlExamineResultHealthCheck(string connectionString)
            : this(connectionString, testQuery: _defaultTestQuery)
        {
        }

        public SqlExamineResultHealthCheck(string connectionString, string testQuery)
        {
            ConnectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
            TestQuery = testQuery;
        }

        public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default(CancellationToken))
        {
            var returnValue = HealthCheckResult.Healthy();
            using (var connection = new SqlConnection(ConnectionString))
            {
                try
                {
                    await connection.OpenAsync(cancellationToken);

                    if (TestQuery != null)
                    {
                        var command = connection.CreateCommand();
                        command.CommandText = TestQuery;

                        var result = await command.ExecuteScalarAsync(cancellationToken);
                        if(result == null || 1 != (int)result)
                        {
                            returnValue = new HealthCheckResult(status: context.Registration.FailureStatus);
                        }
                    }
                }
                catch (DbException ex)
                {
                    returnValue = new HealthCheckResult(status: context.Registration.FailureStatus, exception: ex);
                }
            }

            return returnValue;
        }
    }
}

startup.cs

services.AddHealthChecks()
                    .AddDbContextCheck<ApplicationDbContext>("Db Context", Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus.Unhealthy)                    
                    .AddTypeActivatedCheck<SqlExamineResultHealthCheck>("Db Stored Procedure Call", Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus.Degraded, Configuration.GetConnectionString("Connection"), @"DECLARE	@return_value int

EXEC    @return_value = [dbo].[CHECK_SERVER]
    @pSRC_DB = 1

SELECT  'Return Value' = @return_value")
;