Question

Does anyone know how best to determine the specific underlying cause of this exception?

Consider a WCF service that is supposed to use Powershell 2.0 remoting to execute MSBuild on remote machines. In both cases the scripting environments are being called in-process (via C# for Powershell and via Powershell for MSBuild), rather than ‘shelling-out’ – this was a specific design decision to avoid command-line hell as well as to enable passing actual objects into the Powershell script.

An abridged version of the Powershell script that calls MSBuild is shown below:

function Run-MSBuild
{
    [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.Build.Engine")

    $engine = New-Object Microsoft.Build.BuildEngine.Engine
    $engine.BinPath = "C:\Windows\Microsoft.NET\Framework\v3.5"

    $project = New-Object Microsoft.Build.BuildEngine.Project($engine, "3.5")
    $project.Load("deploy.targets")
    $project.InitialTargets = "DoStuff"

    # Process the input object
    while ($input.MoveNext())
    {
        # Set MSBuild Properties & Item
    }


    # Optionally setup some loggers (have also tried it without any loggers)
    $consoleLogger = New-Object Microsoft.Build.BuildEngine.ConsoleLogger
    $engine.RegisterLogger($consoleLogger)

    $fileLogger = New-Object Microsoft.Build.BuildEngine.FileLogger
    $fileLogger.Parameters = "verbosity=diagnostic"
    $engine.RegisterLogger($fileLogger)


    # Run the build - this is the line that throws a CmdletInvocationException
    $result = $project.Build()

    $engine.Shutdown()
}

When running the above script from a PS command prompt it all works fine. However, as soon as the script is executed from C# it fails with the above exception.

The C# code being used to call Powershell is shown below (remoting functionality removed for simplicity’s sake):

// Build the DTO object that will be passed to Powershell
dto = SetupDTO()

RunspaceConfiguration runspaceConfig = RunspaceConfiguration.Create();
using (Runspace runspace = RunspaceFactory.CreateRunspace(runspaceConfig))
{
    runspace.Open();

    IList errors;
    using (var scriptInvoker = new RunspaceInvoke(runspace))
    {
        // The Powershell script lives in a file that gets compiled as an embedded resource
        TextReader tr = new StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream("MyScriptResource"));
        string script = tr.ReadToEnd();

        // Load the script into the Runspace
        scriptInvoker.Invoke(script);

        // Call the function defined in the script, passing the DTO as an input object
        var psResults = scriptInvoker.Invoke("$input | Run-MSBuild", dto, out errors);
    }
}

NOTE: The overload of the Invoke() method allows you to pass in an IEnumerable object and it takes care of instantiating an enumerator to in the Powershell variable ‘$input’ – this then gets passed into the script via the pipeline. Here are some supporting links:

• http://msdn.microsoft.com/en-us/library/ms569104(VS.85).aspx
• http://knicksmith.blogspot.com/2007/03/managing-exchange-2007-recipients-with.html (jump to the ‘Passing an Input Object to the Runspace’ section)

Assuming that the issue was related to MSBuild outputting something that the Powershell runspace can’t cope with, I have also tried the following variations to the second .Invoke() call:

var psResults = scriptInvoker.Invoke("$input | Run-MSBuild | Out-String", dto, out errors);
var psResults = scriptInvoker.Invoke("$input | Run-MSBuild | Out-Null", dto, out errors);
var psResults = scriptInvoker.Invoke("Run-MSBuild | Out-String");
var psResults = scriptInvoker.Invoke("Run-MSBuild | Out-String");
var psResults = scriptInvoker.Invoke("Run-MSBuild | Out-Null");
var psResults = scriptInvoker.Invoke("Run-MSBuild");

Note how the underlying issue still occurs irrespective of whether an input object is used.

I’ve also looked at using a custom PSHost (based on this sample: http://blogs.msdn.com/daiken/archive/2007/06/22/hosting-windows-powershell-sample-code.aspx), but during debugging I was unable to see any ‘interesting’ calls to it being made.

Do the great and the good of Stackoverflow have any insight that might save my sanity?

Answer 1

I can get the following code to work but I get a warning that MSBUILD engine wants to be run on a STA thread. Unfortunately the thread created by the PowerShell engine to execute the script is MTA. That said, my little sample works:

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Management.Automation;
using System.Collections;

namespace RunspaceInvokeExp
{
    class Program
    {
        static void Main()
        {
            var script = @"
function Run-MSBuild 
{ 
    [System.Reflection.Assembly]::LoadWithPartialName(""Microsoft.Build.Engine"") 

    $engine = New-Object Microsoft.Build.BuildEngine.Engine 
    $engine.BinPath = ""C:\Windows\Microsoft.NET\Framework\v3.5"" 

    $project = New-Object Microsoft.Build.BuildEngine.Project($engine, ""3.5"") 
    $project.Load(""deploy.targets"") 
    $project.InitialTargets = ""DoStuff"" 

    # Process the input object 
    while ($input.MoveNext()) 
    { 
        # Set MSBuild Properties & Item 
    } 

    # Optionally setup some loggers (have also tried it without any loggers) 
    $consoleLogger = New-Object Microsoft.Build.BuildEngine.ConsoleLogger 
    $engine.RegisterLogger($consoleLogger) 

    $fileLogger = New-Object Microsoft.Build.BuildEngine.FileLogger 
    $fileLogger.Parameters = ""verbosity=diagnostic"" 
    $engine.RegisterLogger($fileLogger) 

    # Run the build - this is the line that throws a CmdletInvocationException 
    $result = $project.Build() 

    $engine.Shutdown() 
} 
";
            using (var invoker = new RunspaceInvoke())
            {
                invoker.Invoke(script);
                IList errors;
                Collection<PSObject> results = invoker.Invoke(@"$input | Run-MSBuild", new[] {0}, out errors);
                Array.ForEach<PSObject>(results.ToArray(), Console.WriteLine);
            }
        }
    }
}

Which line of your C# code fails? Also, can you post some of the specifics from the exception. You can work around the MTA thread issue by doing something like this:

using System;
using System.Collections;
using System.Collections.ObjectModel;
using System.Linq;
using System.Management.Automation;
using System.Management.Automation.Runspaces;

namespace RunspaceInvokeExp
{
    class Program
    {
        [STAThread]
        static void Main()
        {
            var script = @"
function Run-MSBuild 
{ 
    [System.Reflection.Assembly]::LoadWithPartialName(""Microsoft.Build.Engine"") 

    $engine = New-Object Microsoft.Build.BuildEngine.Engine 
    $engine.BinPath = ""C:\Windows\Microsoft.NET\Framework\v3.5"" 

    $project = New-Object Microsoft.Build.BuildEngine.Project($engine, ""3.5"") 
    $project.Load(""deploy.targets"") 
    $project.InitialTargets = ""DoStuff"" 

    # Process the input object 
    while ($input.MoveNext()) 
    { 
        # Set MSBuild Properties & Item 
    } 

    # Optionally setup some loggers (have also tried it without any loggers) 
    $consoleLogger = New-Object Microsoft.Build.BuildEngine.ConsoleLogger 
    $engine.RegisterLogger($consoleLogger) 

    $fileLogger = New-Object Microsoft.Build.BuildEngine.FileLogger 
    $fileLogger.Parameters = ""verbosity=diagnostic"" 
    $engine.RegisterLogger($fileLogger) 

    # Run the build - this is the line that throws a CmdletInvocationException 
    $result = $project.Build() 

    $engine.Shutdown() 
} 

Run-MSBuild
";

            Runspace runspace = RunspaceFactory.CreateRunspace();
            Runspace.DefaultRunspace = runspace;
            runspace.Open();

            EngineIntrinsics engine = runspace.SessionStateProxy.
                GetVariable("ExecutionContext") as EngineIntrinsics;
            ScriptBlock scriptblock = 
                engine.InvokeCommand.NewScriptBlock(script);
            Collection<PSObject> results = scriptblock.Invoke(new[] { 0 });
            Array.ForEach<PSObject>(results.ToArray(), Console.WriteLine);

            runspace.Close(); // Really should be in a finally block
        }
    }
}