Using WPF from PowerShell...

I have seen all kind of examples where Windows Forms is used from PowerShell.
Looked like fun so I tried to do the same with Windows Presentatio Foundation
(WPF).

My code:

function LoadAssembly([string]$assembly)
{
$assemblyInfo = [System.Reflection.Assembly]::LoadWithPartialName($assembly)
if($assemblyInfo -eq $null)
{
"unable to load assembly $assembly!"
exit -1
}
}

LoadAssembly "PresentationCore"
LoadAssembly "PresentationFramework"
$form = new-object System.Windows.Window
$form.Title = "hello"
$form.Show

The assemblies are found, but on construction of the System.Windows.Window
object the constructor throws an exception:

New-Object : Exception calling ".ctor" with "0" argument(s): "The calling
thread must be STA, because many UI components require this."

Is it possible to get PowerShell in STA moed, or do I need to create a
CmdLet where a new thread is started in STA.

I have seen code like this in CmsLets to solve this problem:

protected override void BeginProcessing()
{
Thread queryThread = new Thread(ExecuteQuery);
queryThread.SetApartmentState(ApartmentState.STA);
queryThread.Start();
queryThread.Join();
}

I've been waiting for someone to ask this :-) The problem is that the
current PowerShell host defaults to using MTA threads and there's no way to
change it. I don't even think you can work around this using a cmdlet in any
useful way because you'd have to create an new STA thread to show the UI but
there's no way to bind PowerShell actions to the controls.

So you have to write a new host. This actually turns out not to be that
difficult. Here's a simple winexe host that can run scripts that use XAML.
Compile this file into an exe "stahost.exe" and then you can run scripts
that use XAML by doing:

../stahost myxamlscript.ps1

This host takes advantage of the DefaultRunspace property and the fact that
you can retrieve the $ExecutionContext from the runtime to build and
execute scriptblocks on the host STA thread. (As always, this code is
provided "AS IS" with no warranties.) The host code along with an example
script that uses XAML are attached. (The XAML example is the calculator
example that is distrubuted with the WPF SDK hacked up to be a PS script.

-bruce


--------------------------------------cut
here-----------------------------------
/*

# PowerShell commands to compile this file
$SMA =
"$env:windir\assembly\GAC_MSIL\System.Management.Automation\1.0.0.0__31bf3856ad364e35\System.Management.Automation.dll"
csc /target:winexe /debug /r:$SMA stahost.cs

*/
using System;
using System.Collections.ObjectModel;
using System.Text;
using System.IO;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using System.Windows.Forms;

class PowerShell
{
[STAThread]
public static void Main(string[] args)
{
if (args.Length != 1)
{
MessageBox.Show("stahost: you must specify a script to run.");
Environment.Exit(2);
}

try {
string script = File.ReadAllText(args[0]);

Runspace rs = RunspaceFactory.CreateRunspace();

// Must set the default runspace
Runspace.DefaultRunspace = rs;
rs.Open();
EngineIntrinsics engine = rs.SessionStateProxy
.GetVariable("ExecutionContext") as EngineIntrinsics;

// Now run the scriptblock on the Main (STA) thread
// instead of the engine thread
// which is MTA
ScriptBlock sb = engine.InvokeCommand.NewScriptBlock(script);
sb.Invoke(args);
}
catch (Exception e)
{
string position = "<script location unknown";
RuntimeException re = e as RuntimeException;
if (re != null)
{
position = re.ErrorRecord.InvocationInfo.PositionMessage;
}
MessageBox.Show(
String.Format(
"stahost: error running script {0}\n{1}\n{2}\n{3}",
args[0], e.Message, position, e));
}
}
}

--------------------------------------cut
here-----------------------------------

--
Bruce Payette [MSFT]
Windows PowerShell Technical Lead
Microsoft Corporation
This posting is provided "AS IS" with no warranties, and confers no rights.



"Serge van den Oever [Macaw]"
<SergevandenOeverMacaw@discussions.microsoft.com> wrote in message
news:3CC9C966-4ADB-4337-9EF1-7F4281132B8D@microsoft.com...
>I have seen all kind of examples where Windows Forms is used from
>PowerShell.
> Looked like fun so I tried to do the same with Windows Presentatio
> Foundation
> (WPF).
>
> My code:
>
> function LoadAssembly([string]$assembly)
> {
> $assemblyInfo =
> [System.Reflection.Assembly]::LoadWithPartialName($assembly)
> if($assemblyInfo -eq $null)
> {
> "unable to load assembly $assembly!"
> exit -1
> }
> }
>
> LoadAssembly "PresentationCore"
> LoadAssembly "PresentationFramework"
> $form = new-object System.Windows.Window
> $form.Title = "hello"
> $form.Show
>
> The assemblies are found, but on construction of the System.Windows.Window
> object the constructor throws an exception:
>
> New-Object : Exception calling ".ctor" with "0" argument(s): "The calling
> thread must be STA, because many UI components require this."
>
> Is it possible to get PowerShell in STA moed, or do I need to create a
> CmdLet where a new thread is started in STA.
>
> I have seen code like this in CmsLets to solve this problem:
>
> protected override void BeginProcessing()
> {
> Thread queryThread = new Thread(ExecuteQuery);
> queryThread.SetApartmentState(ApartmentState.STA);
> queryThread.Start();
> queryThread.Join();
> }

Hi Bruce,

Thanks for following up on this one! It is an interesting possibility if we
could levarage WPF within our powershell scripts!

I tried out your application, but did not get it working.

It doesn't seem to execute any script. I first tried my WPF script, didn't
work.
Script with just Write-Host "hello world" does not work, migght be that
output pipes ar enot connected or something.
Script with New-Item c:\test.txt does not work.

So seems that scripts don't work at all...

Any ideas?

Serge


"Bruce Payette [MSFT]" wrote:

> I've been waiting for someone to ask this :-) The problem is that the
> current PowerShell host defaults to using MTA threads and there's no way to
> change it. I don't even think you can work around this using a cmdlet in any
> useful way because you'd have to create an new STA thread to show the UI but
> there's no way to bind PowerShell actions to the controls.
>
> So you have to write a new host. This actually turns out not to be that
> difficult. Here's a simple winexe host that can run scripts that use XAML.
> Compile this file into an exe "stahost.exe" and then you can run scripts
> that use XAML by doing:
>
> ../stahost myxamlscript.ps1
>
> This host takes advantage of the DefaultRunspace property and the fact that
> you can retrieve the $ExecutionContext from the runtime to build and
> execute scriptblocks on the host STA thread. (As always, this code is
> provided "AS IS" with no warranties.) The host code along with an example
> script that uses XAML are attached. (The XAML example is the calculator
> example that is distrubuted with the WPF SDK hacked up to be a PS script.
>
> -bruce
>
>
> --------------------------------------cut
> here-----------------------------------
> /*
>
> # PowerShell commands to compile this file
> $SMA =
> "$env:windir\assembly\GAC_MSIL\System.Management.Automation\1.0.0.0__31bf3856ad364e35\System.Management.Automation.dll"
> csc /target:winexe /debug /r:$SMA stahost.cs
>
> */
> using System;
> using System.Collections.ObjectModel;
> using System.Text;
> using System.IO;
> using System.Management.Automation;
> using System.Management.Automation.Runspaces;
> using System.Windows.Forms;
>
> class PowerShell
> {
> [STAThread]
> public static void Main(string[] args)
> {
> if (args.Length != 1)
> {
> MessageBox.Show("stahost: you must specify a script to run.");
> Environment.Exit(2);
> }
>
> try {
> string script = File.ReadAllText(args[0]);
>
> Runspace rs = RunspaceFactory.CreateRunspace();
>
> // Must set the default runspace
> Runspace.DefaultRunspace = rs;
> rs.Open();
> EngineIntrinsics engine = rs.SessionStateProxy
> .GetVariable("ExecutionContext") as EngineIntrinsics;
>
> // Now run the scriptblock on the Main (STA) thread
> // instead of the engine thread
> // which is MTA
> ScriptBlock sb = engine.InvokeCommand.NewScriptBlock(script);
> sb.Invoke(args);
> }
> catch (Exception e)
> {
> string position = "<script location unknown";
> RuntimeException re = e as RuntimeException;
> if (re != null)
> {
> position = re.ErrorRecord.InvocationInfo.PositionMessage;
> }
> MessageBox.Show(
> String.Format(
> "stahost: error running script {0}\n{1}\n{2}\n{3}",
> args[0], e.Message, position, e));
> }
> }
> }
>
> --------------------------------------cut
> here-----------------------------------
>
> --
> Bruce Payette [MSFT]
> Windows PowerShell Technical Lead
> Microsoft Corporation
> This posting is provided "AS IS" with no warranties, and confers no rights.
>
>
>
> "Serge van den Oever [Macaw]"
> <SergevandenOeverMacaw@discussions.microsoft.com> wrote in message
> news:3CC9C966-4ADB-4337-9EF1-7F4281132B8D@microsoft.com...
> >I have seen all kind of examples where Windows Forms is used from
> >PowerShell.
> > Looked like fun so I tried to do the same with Windows Presentatio
> > Foundation
> > (WPF).
> >
> > My code:
> >
> > function LoadAssembly([string]$assembly)
> > {
> > $assemblyInfo =
> > [System.Reflection.Assembly]::LoadWithPartialName($assembly)
> > if($assemblyInfo -eq $null)
> > {
> > "unable to load assembly $assembly!"
> > exit -1
> > }
> > }
> >
> > LoadAssembly "PresentationCore"
> > LoadAssembly "PresentationFramework"
> > $form = new-object System.Windows.Window
> > $form.Title = "hello"
> > $form.Show
> >
> > The assemblies are found, but on construction of the System.Windows.Window
> > object the constructor throws an exception:
> >
> > New-Object : Exception calling ".ctor" with "0" argument(s): "The calling
> > thread must be STA, because many UI components require this."
> >
> > Is it possible to get PowerShell in STA moed, or do I need to create a
> > CmdLet where a new thread is started in STA.
> >
> > I have seen code like this in CmsLets to solve this problem:
> >
> > protected override void BeginProcessing()
> > {
> > Thread queryThread = new Thread(ExecuteQuery);
> > queryThread.SetApartmentState(ApartmentState.STA);
> > queryThread.Start();
> > queryThread.Join();
> > }
>
>
>