WPF和PowerShell-将变量从PS传递到C＃或修改值

Question

I need to perform a validation using PowerShell and based on the result, execute an action in the WPF Application. I know I can modify TextBlocks from PowerShell but when I try to modify the value of a WPF variable from within PowerShell nothing happens.

Here's an example.

MainWindow.xaml:

    <Window x:Class="Test.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Test"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <TextBlock x:Name="textBlock" HorizontalAlignment="Left" Margin="74,76,0,0" TextWrapping="Wrap" Text="false" VerticalAlignment="Top" Height="177" Width="371"/>
    </Grid>
</Window>

MainWindow.xaml.cs:

using System;
using System.Windows;
using System.Windows.Controls;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using System.Text.RegularExpressions;
using System.IO;

namespace Test
{
    public partial class MainWindow : Window
    {
        private bool exists = false;

        public MainWindow()
        {
            InitializeComponent();

            // Setup PowerShell Environment
            Runspace runSpace = RunspaceFactory.CreateRunspace();
            runSpace.ThreadOptions = PSThreadOptions.UseCurrentThread;
            runSpace.Open();
            runSpace.SessionStateProxy.SetVariable("exists", exists);
            PowerShell ps = PowerShell.Create();
            ps.Runspace = runSpace;
            string check = "$exists = true";
            ps.AddScript(check);
            // Execute
            ps.Invoke();
            runSpace.Close();

            if (exists == true)
            {
                textBlock.Text = "It is true!";
            }
        }
    }
}

How can I modify the C# / WPF variable from within PowerShell after doing some validation? Is that even possible?

I don't want to have to create random textblocks / labels / textboxes for temporary variables.

Answer 1

First of all, exists is a value type. To update exists from PowerShell you would have to pass it by reference to your PowerShell script. I may be wrong but it seems unlikely that that is possibly. Even if it were possible I still would not recommend it. Manipulating state like that just seems gross. I think a better approach is to pass the data that you want to validate to your PowerShell script and return the result of the validation back to C#. You can modify your variable state in C# based on that result.

Here is a slightly modified version of your code that I ran in LinqPad with the output:

var exists = true;
Runspace runSpace = RunspaceFactory.CreateRunspace();
runSpace.ThreadOptions = PSThreadOptions.UseCurrentThread;
runSpace.Open();

PowerShell ps = PowerShell.Create();
ps.Runspace = runSpace;
string validation = @"
    # Perform some validation.

    # For the purposes of this demonstration I am going to pretend
    # that validation failed and set 'result' to false.
    $result = $false

    # Return 'result'
    $result
";
ps.AddScript(validation);

// Write the state of `exists` to the console before invoking PowerShell.
Console.WriteLine("exists: " + exists.ToString());

// Execute
var result = ps.Invoke();

// Update exists based on the result of the validation.
exists = bool.Parse(result[0].ToString());

// Or you can use 'GetVariable' to get the result back from PowerShell:
// exists = bool.Parse(runSpace.SessionStateProxy.GetVariable("result").ToString());

// Write the state to the console after invoking PowerShell.
Console.WriteLine("exists: " + exists.ToString());

And here is the result written to the console:

exists: True
exists: False

Answer 2

Using Mike's suggestion I managed to get the variable from PS withouth even having to map it. Like so:

using System;
using System.Windows;
using System.Windows.Controls;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using System.Text.RegularExpressions;
using System.IO;

namespace Test
{
    public partial class MainWindow : Window
    {
        public bool itExists = false;

        public MainWindow()
        {
            InitializeComponent();

            // Setup PowerShell Environment
            Runspace runSpace = RunspaceFactory.CreateRunspace();
            runSpace.ThreadOptions = PSThreadOptions.UseCurrentThread;
            runSpace.Open();
            PowerShell ps = PowerShell.Create();
            ps.Runspace = runSpace;
            string check = "$itExists = $TRUE";
            ps.AddScript(check);
            // Execute
            ps.Invoke();

            var result = runSpace.SessionStateProxy.PSVariable.GetValue("itExists").ToString();

            runSpace.Close();

            itExists = result.Equals("True");

            if (itExists)
            {
                textBlock.Text = "It is true!";
            }
        }
    }
}