A Command Is Already In Progress

I am attempting to run a background worker for a web app that I am developing. I am using Npgsql as my EF Core provider.

For clarification, I have injected my DbContext with a Transient lifetime, and have allowed Pooling in my connection string, however, whenever I try to test it I get the following error:

Npgsql.NpgsqlOperationInProgressException: A command is already in progress: [My Query Here]

I have my Program Class Set up as such:

public class Program { public static void Main(string[] args) { CreateHostBuilder(args).Build().Run(); } public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureServices((hostContext, services) => { // Get the configuration IConfiguration config = hostContext.Configuration; // DbContext services.AddDbContext<MyDbContext>(options => options.UseNpgsql(config.GetConnectionString("PostgreSQLString")), ServiceLifetime.Transient); services.AddHostedService<Worker>(); services.AddScoped<IDTOService, BackgroundDTOService>(); }); } 

Which then leads to my Worker class

public class Worker : BackgroundService { private Logger logger; public Worker(IServiceProvider services, IConfiguration configuration) { this.Services = services; var optionsBuilder = new DbContextOptionsBuilder<MyDbContext>(); optionsBuilder.UseNpgsql(configuration.GetConnectionString("PostgreSQLString")); var context = new StatPeekContext(optionsBuilder.Options); this.logger = new Logger(new LogWriter(context)); } public IServiceProvider Services { get; } protected override async Task ExecuteAsync(CancellationToken stoppingToken) { this.logger.LogInformation("ExecuteAsync in Worker Service is running."); await this.DoWork(stoppingToken); } private async Task DoWork(CancellationToken stoppingToken) { using (var scope = Services.CreateScope()) { var context = scope.ServiceProvider.GetRequiredService<MyDbContext>(); var dtoService = scope.ServiceProvider.GetRequiredService<IDTOService>(); await dtoService.ProcessJSON(stoppingToken); } } public override async Task StopAsync(CancellationToken cancellationToken) { this.logger.LogInformation("Worker service is stopping."); await Task.CompletedTask; } } 

which leads to my BackGroundDTOService

public class BackgroundDTOService : IDTOService { private int executionCount = 0; private Logger logger; private MyDbContext context; private DbContextOptionsBuilder<MyDbContext> optionsBuilder; public BackgroundDTOService(IConfiguration configuration, MyDbContext context) { this.optionsBuilder = new DbContextOptionsBuilder<MyDbContext>(); this.optionsBuilder.UseNpgsql(configuration.GetConnectionString("PostgreSQLString")); this.logger = new Logger(new LogWriter(new MyDbContext(this.optionsBuilder.Options))); this.context = context; } public async Task ProcessJSON(CancellationToken stoppingToken) { while (!stoppingToken.IsCancellationRequested) { this.executionCount++; this.logger.LogInformation($"DTO Service is working. Count: {this.executionCount}"); this.ProcessTeams(); await Task.Delay(TimeSpan.FromSeconds(1), stoppingToken); } } public void ProcessTeams() { // Add Any Franchises that don't exist var franchiseDumps = this.context.RequestDumps.Where(rd => rd.Processed == false && rd.DumpType == "leagueteams"); foreach (RequestDump teamDump in franchiseDumps) { var league = this.context.Leagues.Include(l => l.Franchises).FirstOrDefault(l => l.Id == teamDump.LeagueID); var teams = Jeeves.GetJSONFromKey<List<DTOTeam>>(teamDump.JsonDump, "leagueTeamInfoList"); foreach (DTOTeam team in teams) { this.UpdateFranchise(team, league); } this.logger.LogInformation($"DTO Service Processed League Teams on count {this.executionCount}"); } this.context.SaveChanges(); } 

The error appears to occur immediately after snagging franchiseDumps when it tries to get league

2 Answers

Could you try materialising the query:

 var franchiseDumps = this.context.RequestDumps.Where(rd => rd.Processed == false && rd.DumpType == "leagueteams").ToList(); 

I had the same issue and I realized that PostgreSQL doesn't support Multiple Active Result Sets (MARS) compare to MSSQL.

An alternative way that worked for me to fetch objects with foreign key:

IEnumerable<Expense> objList = _db.Expenses; foreach (var obj in objList.ToList()) { obj.ExpenseCategory = _db.ExpenseCategories.FirstOrDefault(u => u.Id == obj.ExpenseCategoryId); }