Getting “The connection does not support MultipleActiveResultSets” in a ForEach with async-await

Question

I have the following code using Dapper.SimpleCRUD :

var test = new FallEnvironmentalCondition[] {
    new FallEnvironmentalCondition {Id=40,FallId=3,Environm         


        

Answer 1

That code starts a Task for each item in the list, but does not wait for the each task to complete before starting the next one. Inside each Task it waits for the update to complete. Try

 Enumerable.Range(1, 10).ToList().ForEach(async i => await Task.Delay(1000).ContinueWith(t => Console.WriteLine(DateTime.Now)));

Which is equivalent to

    foreach (var i in Enumerable.Range(1, 10).ToList() )
    {
        var task = Task.Delay(1000).ContinueWith(t => Console.WriteLine(DateTime.Now));
    }

If you're in a non-async method you will have to Wait(), not await each task. EG

    foreach (var i in Enumerable.Range(1, 10).ToList() )
    {
        var task = Task.Delay(1000).ContinueWith(t => Console.WriteLine(DateTime.Now));
        //possibly do other stuff on this thread
        task.Wait(); //wait for this task to complete
    }