Building Powershell GUIs that won’t freeze when you use them

A few days ago I wrote about how important I think it is that you build a GUI for your scripts if they are to be used by anoyone else.

If you have ever built a GUI using Powershell however, you know there is a problem with it that I didn’t mention, that is, whenever your script is actually doing anything the GUI will freeze and windows will tell you it isn’t responding. This is not good as most users will then try to close it and try again. We don’t want that.

The reason this happens is because you are running your form (GUI) and logic in the same thread, something you should never do, problem is, Powershells support for multithreading is limited at best.

In the last post I also talked about my module EasyGUI and mentioned that there are features I wouldnt go in to in that post, one of those features is an easy way to use threads.

There are two ways to use threads in EasyGUI, I go through both of them below as well as a tip on how I prefer to use them.

Method 1.

Passing in a scriptblock to the thread, here I am creating it on the fly but you could also store the scriptblock in a variable and pass that to the function instead

New-Thread {
    0..60|Foreach-Object{
        $SYNC.myLabel.Text = $_
    }
}

Method 2.

You could also write the code for the thread in a separate script file and then pass that to the New-Thread function like this

New-Thread "D:\Program\Powershell\myThread.ps1"

One thing to be aware of is that the threads will start running emediatly when you create them. Often you might not want that. What I usually do is create the threads inside a scriptblock that I store in a variable, then when I need the tread to run I run that scriptblock. That would look something like this.

$myThread = {
    New-Thread {
        0...60|Foreach-Object{
            $SYNC.myLabel.Text = $_
        }
    }
}

#Now it's time to run the thread, simply type the & sign and then the variable containing the scriptblock
&$myThread

$SYNC ? Where did that come from?

Noticed that did you?

This is a variable that’s automatically created when you initialize the EasyGUI module. It’s a hashtable that’s synced between all threads so you can communicate between them. In the examples you see that I am using $SYNC.myLabel. This is created in the GUI like this.

$SYNC.myLabel = New-Label @{
    Location = "15, 15"
}

or like this

$myLabel = New-Label @{
    Location = "15, 15"
}
$SYNC.myLabel = $myLabel

If you want to see a complete example of a GUI script with threading implemented there is an example availiable in the Easy GUI repository.

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Writing Powershell GUIs the easy way

One of the most important tools for any IT professional or service desk technician that works in a Windows environment is without a doubt Powershell. Not only is it extremely powerful but it is also very fun to work with if you ask me.

One of the great features of Powershell that I feel doesn’t get enough love from the Powershell community is the ability to write scripts with graphical user interfaces. Yeah, yeah, I know, you want to be able to do a quick change in the script and then rerun it inside ISE and anyone that doesn’t know how to use a console shouldn’t be in IT anyway, right? Wrong!

It is my firm belief that a clear and easy to use interface is just as important as the logic itself when you write a script that is going to be used by someone else. For most people, that means the interface needs to be graphical. I base this belief on having worked in an IT department at a large company for several years as well as maintained the Booksonic project since the start in late 2015. If you want to change my mind, feel free to try and do so in the comments below.

Now with that out of the way I will stop trying to convince you about writing user interfaces for your scripts, the fact that you are reading this post probably means that you are already doing it or thinking about doing it. Instead I am going to focus on how to do it in a way so the code is easy to read and maintain even once you start writing more complex UIs.

When I first started writing powershell I noticed that most examples of people writing powershell UIs get really messy real fast.

A typical example you may find online looks something like this

Add-Type -AssemblyName System.Windows.Forms
Add-Type -Name Window -Namespace Console -MemberDefinition '
        [DllImport("Kernel32.dll")]
        public static extern IntPtr GetConsoleWindow();     
        [DllImport("user32.dll")]
        public static extern bool ShowWindow(IntPtr hWnd, Int32 nCmdShow);

[Console.Window]::ShowWindow([Console.Window]::GetConsoleWindow(), 0)       '

$font = New-Object System.Drawing.Font("Times New Roman",24,[System.Drawing.FontStyle]::Bold)

$label = New-Object System.Windows.Forms.Label
$label.Cursor = [System.Windows.Forms.Cursors]::Hand
$label.Text = "Click me to open popeen.com" 
$label.BackColor = "Transparent"
$label.ForeColor = "Blue" 
$label.AutoSize = $true
$label.Location.X = 15
$label.Location.Y = 15
$label.Add_Click = { Start-Process -FilePath iexplore  -ArgumentList "https://popeen.com" }

$form = New-Object system.Windows.Forms.Form
$form.Width = 600
$form.Height = 200
$form.Text = "Example form"
$form.Font = $font
$form.Controls.Add($label)
$form.ShowDialog() 

Now functionally speaking there is nothing wrong with that script and in fact it may not look that bad either but remember, all we have done is created a window and added one label to it. Imagine how cluttered this would become once you started doing some more advanced UIs. A better way to write the above that I have actually never seen anyone use other than me and some of my colleages would be using -Properties like this.

Add-Type -AssemblyName System.Windows.Forms
Add-Type -Name Window -Namespace Console -MemberDefinition '
        [DllImport("Kernel32.dll")]
        public static extern IntPtr GetConsoleWindow();     
        [DllImport("user32.dll")]
        public static extern bool ShowWindow(IntPtr hWnd, Int32 nCmdShow);

[Console.Window]::ShowWindow([Console.Window]::GetConsoleWindow(), 0)

$label = New-Object System.Windows.Forms.Label -Properties @{
    Cursor = [System.Windows.Forms.Cursors]::Hand
    Text = "Click me to open popeen.com" 
    BackColor = "Transparent"
    ForeColor = "Blue"
    AutoSize = $true
    Location = "15, 15"
    Add_Click = { Start-Process -FilePath iexplore  -ArgumentList "https://popeen.com" }
}

$form = New-Object system.Windows.Forms.Form -Properties @{
    Size = "600, 200"
    Text = "Example form"
    Font = New-Object System.Drawing.Font("Times New Roman", 24, [System.Drawing.FontStyle]::Bold)
}
$form.Controls.Add($label)
$form.ShowDialog() 

While this takes up about the same space it looks much better right? This way a quick glance at the code gives you a much better understanding of what it is you are looking at.

If you choose to stop reading here and start writing your UIs in this way I beleive you will have a much easier time maintaining that script then you had before. However, I have taken it a step further in my scripts.

When I write a script I use a specific framework that makes the code even quicker to read and also includes some other nice features that I won’t go in to in this post but might make future posts about. One of the most important parts of this framework is a module I call EasyGUI and that you can download at https://gitlab.com/Popeen/EasyGUI

This module builds on the second example above and simplifies it even more. It also includes some other cool stuff that I also won’t go in to here but again, might make another post about. If we decided to use EasyGUI to write the example above it would look like this

Import-Module EasyGUI

Initialize-EasyGUI
Hide-Console

$form = New-Form @{
    Size = "600, 200"
    Text = "Example form"
    Font = New-Font -Font "Times New Roman" -Size 24 -Style $FONTSTYLE.Bold
}

$label = New-Label @{
    Cursor = $CURSOR.Hand
    Text = "Click me to open popeen.com" 
    BackColor = "Transparent"
    ForeColor = "Blue"
    AutoSize = $true
    Location = "15, 15"
    Add_Click = { Start-Process -FilePath iexplore  -ArgumentList "https://popeen.com" }
}

$form.Controls.Add($label)

Show-Form $form
Stop-Console 

I dont know about you but I find that to be much more readable then the first example we looked at, especially when you are working with a lot more then just a label.

It should be noted that not every forms object is in EasyGUI yet as I add them when I need them but adding them yourself should be very easy even for someone new to Powershell and if not just post a comment below and let me know what object you would like added.

I would love to hear your thoughts on this, is it something you would ever use or do you think I’m just talking rubbish when I say that UIs are this important or that a simple module like this can make it a lot more quick, fun and easy to code and maintain UIs.

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