CODEWITHSUNDEEP
c#powershell
Skrymsli
Skrymsli

Reputation: 5313

Why does PowerShell Pipeline.Output.ReadToEnd return an empty collection?

Using C# with System.Management.Automation to run a PowerShell command - I'm trying to understand the purpose/intention of the Pipeline.Output property. This code:

class Program
{
    static void Main(string[] args)
    {
        var results = new List<PSObject>();
        var stdout = new List<PSObject>();

        using (var runspace = RunspaceFactory.CreateRunspace())
        {
            runspace.Open();
            using (var pipeline = runspace.CreatePipeline())
            {
                pipeline.Commands.Add(new Command("Get-ChildItem"));

                results.AddRange(pipeline.Invoke());
                stdout.AddRange(pipeline.Output.ReadToEnd());
            }
            runspace.Close();
        }

        Console.WriteLine("results.Count: {0}", results.Count);
        Console.WriteLine("stdout.Count: {0}", stdout.Count);
    }
}

Prints:

results.Count: 7
stdout.Count: 0

I would expect both counts to be 7. The documentation is sparse on Pipeline.Output. Can anyone shed some light on what Pipeline.Output is supposed to be used for? What am I misunderstanding?

Upvotes: 1

Views: 981

Answers (1)

Mathias R. Jessen
Mathias R. Jessen

Reputation: 174445

When you call Invoke() it returns the output immediately - Output only gets populated when you invoke the pipeline asynchronously.

Example, invoking and waiting for maximum a second: 

pipeline.InvokeAsync();
pipeline.Output.WaitHandle.WaitOne(1000);
if(pipeline.PipelineStateInfo.State == PipelineState.Completed) {
    stdout.AddRange(pipeline.Output.ReadToEnd());
}

Or better yet, set up an event handler for the StateChanged event

Upvotes: 2

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