Capturing Powershell output in C# after Pipeline.Invoke throws

Question

I'm running a Powershell test script from a C# application. The script can fail due to a bad cmdlet which causes pipe.Invoke() to throw an exception.

I'm able to capture all the information I need about the exception, but I'd like to be able to display the script's output up to that point. I haven't had any luck since results appears to be null when an exception is thrown.

Is there something I'm missing? Thanks!

m_Runspace = RunspaceFactory.CreateRunspace();
m_Runspace.Open();
Pipeline pipe = m_Runspace.CreatePipeline();
pipe.Commands.AddScript(File.ReadAllText(ScriptFile));
pipe.Commands.Add("Out-String");
try {
   results = pipe.Invoke();
}
catch (System.Exception)
{
   m_Runspace.Close();
   // How can I get to the Powershell output that comes before the exception?
}

Answer 1

The solution I ended up using was to implement our own PSHost to handle PowerShell's output. The initial information for this came from http://community.bartdesmet.net/blogs/bart/archive/2008/07/06/windows-powershell-through-ironruby-writing-a-custom-pshost.aspx in the "Building a custom PS host" section.

In my case it did require using a custom PSHostRawUserInterface as well.

Here's the quick overview of what was done. I've only listed the function I actually implimented, but there's many that are just contain throw new NotImplementedException();

private class myPSHost : PSHost
{
   (Same as what the above link mentions)
}
private class myPSHostUI : PSHostUserInterface
{
   private myPSHostRawUI rawui = new myPSHostRawUI();

   public override void Write // all variations
   public override PSHostRawUserInterface RawUI { get { return rawui; } }

}
private class myPSHostRawUI : PSHostRawUserInterface
{
   public override ConsoleColor ForegroundColor
   public override ConsoleColor BackgroundColor
   public override Size BufferSize
}

Answer 2

I have the same problem. The easiest way to get output when pipe.Invoke() throws an exception is to use Invoke(IEnumerable input, IList output)

Example shows how to get all output, error, waning etc. in the correct order

PowerShell script

Write-Output "Hello world" 
Write-Error "Some error"
Write-Warning "Some warning"
throw "Some exception"

C#

List<string> RunLog = new List<string>(); 

using (System.Management.Automation.PowerShell psInstance = System.Management.Automation.PowerShell.Create())

{
    psInstance.AddScript(_Script);

psInstance.Streams.Error.DataAdded += (sender, args) =>
{
    ErrorRecord err = ((PSDataCollection<ErrorRecord>)sender)[args.Index];
    RunLog.Add($"ERROR: {err}");
};

psInstance.Streams.Warning.DataAdded += (sender, args) =>
{
    WarningRecord warning = ((PSDataCollection<WarningRecord>)sender)[args.Index];
    RunLog.Add($"WARNING: {warning}");
};

... etc ...

var result = new PSDataCollection<PSObject>();
result.DataAdded += (sender, args) =>
{
    PSObject output = ((PSDataCollection<PSObject>)sender)[args.Index];
    RunLog.Add($"OUTPUT: {output}");
};

try
{
    psInstance.Invoke(null, result);
}
catch(Exception ex)
{
    RunLog.Add($"EXCEPTION: {ex.Message}");
}                                                
}