Building a PowerShell GUI (Part 13)

If you would like to read the other parts in this article series please go to:

• Building a PowerShell GUI (Part 1)
• Building a PowerShell GUI (Part 2)
• Building a PowerShell GUI (Part 3)
• Building a PowerShell GUI (Part 4)
• Building a PowerShell GUI (Part 5)
• Building a PowerShell GUI (Part 6)
• Building a PowerShell GUI (Part 7)
• Building a PowerShell GUI (Part 8)
• Building a PowerShell GUI (Part 9)
• Building a PowerShell GUI (Part 10)
• Building a PowerShell GUI (Part 11)
• Building a PowerShell GUI (Part 12)

In my previous article in this series, I showed you how to build a toggle button that could be used to turn a virtual machine on and off. This button even changed colors as a way of reflecting the state of the virtual machine. In this article, I want to wrap up the series by showing you how to construct a GUI that can be used to change a virtual machine’s memory allocation.

The GUI interface already displays the amount of memory that the VM is currently using, but that may not always be the same thing as the memory allocation. For example, a VM that has been allocated 4 GB of memory will show that 0 GB of memory are being consumed if the VM is powered off.

In order to change the VM memory allocation from a GUI, there are a few things that we need to do. First, we need to create a text box that can display memory allocation. We will use this same text box to make changes.

We will also need a control that can be used to submit memory allocation changes. As you may recall, the GUI already contains a button that is reserved for future use. I will use this button as a submit button.

Finally, we will need some code that takes the value that is being submitted through the form and adjusts the virtual machine’s memory accordingly.

So let’s go ahead and get started by creating a text box and populating it with the current memory allocation. In order to keep things nice and tidy, I am also going to create another label and use it to reflect what I am doing. Here is the code for the additional label and for the text box:

# Define Label8 – Memory Allocation Text
$Label8 = New-Object System.Windows.Forms.Label
$Label8.AutoSize = $False
$Label8.Location = new-object System.Drawing.Size(50,160)
$Label8.Size = New-Object System.Drawing.Size(200,20)
$Label8.ForeColor = “Black”
$Label8.Text = “Memory Allocation (MB)”

$Global:TextBox = New-Object System.Windows.Forms.TextBox
$Global:TextBox.Location = New-Object System.Drawing.Size(50,180)
$Global:TextBox.Size = New-Object System.Drawing.Size(200,20)

In addition, I have added a bit of code to my script to add the new label and textbox objects to the display (and remove those objects from the display) when appropriate. I will provide you with the full script at the end of this article.

So the next thing that we need to do is to populate the text box with the amount of memory that is allocated to the currently selected VM. As you may recall from the previous article, the Display-VMInfo function contains a section in which I create variables to store all of the pieces of data that need to be shown for the selected VM. I am going to add a new variable called $MemoryStart to this

section,

and set it equal to the $MemoryStartup property for the selected VM. Here is what the block of code looks like:

# Get Virtual Machine Information
$SelectedVM = Get-VM $ChosenItem
$Global:Name = $SelectedVM.VMName
$State = $SelectedVM.State
$RunTime = $SelectedVM.UpTime
$Memory = $SelectedVM.MemoryAssigned
$CPU = $SelectedVM.ProcessorCount
$MemoryStart = ($SelectedVM.MemoryStartup / 1MB)

Notice that I am telling PowerShell to express the startup memory in megabytes so as to avoid having to deal with large byte strings. This technique makes for a cleaner output.

In addition, I need to display the $MemoryStartup variable’s contents in the text box, so I am going to add a line to the function’s #Create Text section. Here is what the section now looks like:

#Create text
$Label.Text = ‘Virtual Machine Name: ‘ + $Name
$Label4.Text = ‘VM State: ‘ + $State
$Label5.Text = ‘VM Up Time: ‘ + $RunTime
$Label6.Text = ‘Memory Assigned: ‘ + $Memory
$Label7.Text = ‘Virtual CPUs Assigned :’ + $CPU
$Global:TextBox.Text = $MemoryStart

The figure below shows what the GUI interface now looks like. As you can see, the VM’s startup memory is now displayed in a text box. We can even type over the value that is displayed, but right now doing so would not have any effect. If we want to allow memory changes from the GUI, then we need to do a bit of work on the Reserved for Future Use button.

Here is what the GUI currently looks like.

There are two things that we need to do to the Reserved for Future Use button in order to make it functional. First, we have to change the button text to something a bit more descriptive. Second, we will need to change the button’s click action.  This is where things get just a little bit tricky. Here is the code for the button:

# Define Button 4 – This button doesn’t do anything yet, but we will use it eventually.
$Button4 = New-Object System.Windows.Forms.Button
$Button4.Location = New-Object System.Drawing.Size(140,220)
$Button4.Size = New-Object System.Drawing.Size(150,30)
$Button4.BackColor =”LightGray”
$Button4.Text = “Set Startup Memory”
$Button4.Add_Click({$MemoryStart = $TextBox.Text
$CmdStr = “Set-VMMemory ” + $Name +” -StartupBytes ” + $MemoryStart + “MB”
Invoke-Expression $CmdStr
Display-VMInfo $Name})

As you can see in the code block above, changing the button text is really straightforward. However, we are doing something a bit different with the click action than what has been done previously in this series. Rather than executing a single command or calling a function, we are executing multiple commands.

The first of these commands takes whatever value is currently being displayed within the text box, and assigns it to the $MemoryStart variable.

The second command creates a variable named $CmdStr. This variable will store the text that will make up the command to change the virtual machine’s memory. We are essentially performing string manipulation in order to create the command.

The third command uses the Invoke-Expression cmdlet to execute the contents of the $CmdStr variable. This is the line of code that actually causes the virtual machine’s memory to be changed.

The last call simply calls the Display-VMInfo function. This makes for an easy way to refresh the display.

You can see the final output in the figure below.

Here is what the final script looks like in action.

As promised, here is the code for the script in its entirety:

#Load Assemblies
[System.Reflection.Assembly]::LoadWithPartialName(“System.Windows.Forms”) | Out-Null
[System.Reflection.Assembly]::LoadWithPartialName(“System.Drawing”) | Out-Null
$net = New-Object -ComObject Wscript.Network

# Display the Main Screen
Function Display-MainScreen
{
$Form.Controls.Add($ListBox1)
$Form.Controls.Add($Button1)
$Form.Controls.Add($Button2)
$Form.Controls.Add($Label2)
}

# ———- Button Click Actions ——

#Define Return Button Click Function
Function Return-MainScreen
{

$Form.Controls.Remove($Label)
$Form.Controls.Remove($Label3)
$Form.Controls.Remove($Label4)
$Form.Controls.Remove($Label5)
$Form.Controls.Remove($Label6)
$Form.Controls.Remove($Label7)
$Form.Controls.Remove($Label8)
$Form.Controls.Remove($TextBox)
$Form.Controls.Remove($Button3)
$Form.Controls.Remove($Button4)
$Form.Controls.Remove($Button5)
$Form.Controls.Remove($Button6)
$Form.Refresh()
Display-MainScreen
}

#Define OK Button Click Function
Function Display-VMInfo($ChosenItem)
{

#Clear the window
$Form.Controls.Remove($ListBox1)
$Form.Controls.Remove($Label2)
$Form.Controls.Remove($Button1)
$Form.Controls.Remove($Button2)
$Form.Controls.Remove($Button5)
$Form.Controls.Remove($Button6)
$Form.Refresh()

#Create Output
Add-Type -AssemblyName System.Windows.Forms

# Get Virtual Machine Information

$SelectedVM = Get-VM $ChosenItem
$Global:Name = $SelectedVM.VMName
$State = $SelectedVM.State
$RunTime = $SelectedVM.UpTime
$Memory = $SelectedVM.MemoryAssigned
$CPU = $SelectedVM.ProcessorCount
$MemoryStart = ($SelectedVM.MemoryStartup / 1MB)

#Create text
$Label.Text = ‘Virtual Machine Name: ‘ + $Name
$Label4.Text = ‘VM State: ‘ + $State
$Label5.Text = ‘VM Up Time: ‘ + $RunTime
$Label6.Text = ‘Memory Assigned: ‘ + $Memory
$Label7.Text = ‘Virtual CPUs Assigned :’ + $CPU
$Global:TextBox.Text = $MemoryStart

#Display Screen Contents
$Form.Controls.Add($Label)
$Form.Controls.Add($Label4)
$Form.Controls.Add($Label5)
$Form.Controls.Add($Label6)
$Form.Controls.Add($Label7)
$Form.Controls.Add($Label3)
$Form.Controls.Add($Button3)
$Form.Controls.Add($Button4)
$Form.Controls.Add($Label8)
$Form.Controls.Add($TextBox)

If ($State -eq ‘Off’)
{
$Form.Controls.Add($Button5)
}
If ($State -EQ ‘Running’)
{
$Form.Controls.Add($Button6)
}
}

#—— Define All GUI Objects——-

# Define Label – This is a text box object that will display the VM Name
$Label = New-Object System.Windows.Forms.Label
$Label.AutoSize = $False
$Label.Location = new-object System.Drawing.Size(50,50)
$Label.Size = New-Object System.Drawing.Size(200,20)
$Label.ForeColor = “Black”
$label.BackColor = ‘White’

# Define Label2 – The Please Make a Selection Text
$Label2 = New-Object System.Windows.Forms.Label
$Label2.AutoSize = $True
$Label2.Location = new-object System.Drawing.Size(20,50)
$Label2.ForeColor = “DarkBlue”
$Label2.Text = “Please select a virtual machine from the list.”

# Define Label3 – The This is Your Selected Virtual Machine Text
$Label3 = New-Object System.Windows.Forms.Label
$Label3.AutoSize = $True
$Label3.Location = new-object System.Drawing.Size(50,30)
$Label3.ForeColor = “DarkBlue”
$Label3.Text = “Your selected virtual machine:”

# Define Label4 – The This is the VM State label
$Label4 = New-Object System.Windows.Forms.Label
$Label4.AutoSize = $False
$Label4.Location = new-object System.Drawing.Size(50,70)
$Label4.Size = New-Object System.Drawing.Size(200,20)
$Label4.ForeColor = “Black”
$Label4.BackColor = ‘White’

# Define Label5 – The This is the VM up time
$Label5 = New-Object System.Windows.Forms.Label
$Label5.AutoSize = $False
$Label5.Location = new-object System.Drawing.Size(50,90)
$Label5.Size = New-Object System.Drawing.Size(200,20)
$Label5.ForeColor = “Black”
$Label5.BackColor = “White”

# Define Label6 – The This is the VM memory assigned
$Label6 = New-Object System.Windows.Forms.Label
$Label6.AutoSize = $False
$Label6.Location = new-object System.Drawing.Size(50,110)
$Label6.Size = New-Object System.Drawing.Size(200,20)
$Label6.ForeColor = “Black”
$Label6.BackColor = ‘White’

# Define Label7 – The This is the VM virtual CPUs assigned
$Label7 = New-Object System.Windows.Forms.Label
$Label7.AutoSize = $False
$Label7.Location = new-object System.Drawing.Size(50,130)
$Label7.Size = New-Object System.Drawing.Size(200,20)
$Label7.ForeColor = “Black”
$Label7.BackColor = ‘White’

# Define Label8 – Memory Allocation Text
$Label8 = New-Object System.Windows.Forms.Label
$Label8.AutoSize = $False
$Label8.Location = new-object System.Drawing.Size(50,160)
$Label8.Size = New-Object System.Drawing.Size(200,20)
$Label8.ForeColor = “Black”
$Label8.Text = “Memory Allocation (MB)”

$Global:TextBox = New-Object System.Windows.Forms.TextBox
$Global:TextBox.Location = New-Object System.Drawing.Size(50,180)
$Global:TextBox.Size = New-Object System.Drawing.Size(200,20)

# Define List Box – This will display the virtual machines that can be selected
$ListBox1 = New-Object System.Windows.Forms.ListBox
$ListBox1.Location = New-Object System.Drawing.Size(20,80)
$ListBox1.Size = New-Object System.Drawing.Size(260,20)
$ListBox1.Height = 80

# This code populates the list box with virtual machine names
$VirtualMachines = Get-VM
ForEach ($VM in $VirtualMachines)
{
[void] $ListBox1.Items.Add($VM.Name)
}

# Define Button 1  – This is the selection screen’s OK button
$Button1 = new-object System.Windows.Forms.Button
$Button1.Location = new-object System.Drawing.Size(20,170)
$Button1.Size = new-object System.Drawing.Size(70,30)
$Button1.BackColor =”LightGray”
$Button1.Text = “OK”
$Button1.Add_Click({$ChosenItem=$ListBox1.SelectedItem;Display-VMInfo $ChosenItem})

# Define Button 2 – This is the selection screen’s Cancel button
$Button2 = New-Object System.Windows.Forms.Button
$Button2.Location = New-Object System.Drawing.Size(120,170)
$Button2.Size = New-Object System.Drawing.Size(70,30)
$Button2.BackColor =”LightGray”
$Button2.Text = “Cancel”
$Button2.Add_Click({$Form.Close()})

# Define Button 3 – This is the Return to Main Screen button
$Button3 = New-Object System.Windows.Forms.Button
$Button3.Location = New-Object System.Drawing.Size(50,220)
$Button3.Size = New-Object System.Drawing.Size(70,30)
$Button3.BackColor =”LightGray”
$Button3.Text = “Return”
$Button3.Add_Click({Return-MainScreen})

# Define Button 4 – This button doesn’t do anything yet, but we will use it eventually.
$Button4 = New-Object System.Windows.Forms.Button
$Button4.Location = New-Object System.Drawing.Size(140,220)
$Button4.Size = New-Object System.Drawing.Size(150,30)
$Button4.BackColor =”LightGray”
$Button4.Text = “Set Startup Memory”
$Button4.Add_Click({$MemoryStart = $TextBox.Text
$CmdStr = “Set-VMMemory ” + $Name +” -StartupBytes ” + $MemoryStart + “MB”
Invoke-Expression $CmdStr
Display-VMInfo $Name})

# Define Button 5 – This button will be used to start a virtual machine.
$Button5 = New-Object System.Windows.Forms.Button
$Button5.Location = New-Object System.Drawing.Size(140,260)
$Button5.Size = New-Object System.Drawing.Size(150,30)
$Button5.BackColor =”Green”
$Button5.ForeColor =”White”
$Button5.Text = “Start VM”
$Button5.Add_Click({Start-VM $Name | Display-VMInfo $Name})

# Define Button 6 – This button shuts down a virtual machine.
$Button6 = New-Object System.Windows.Forms.Button
$Button6.Location = New-Object System.Drawing.Size(140,260)
$Button6.Size = New-Object System.Drawing.Size(150,30)
$Button6.BackColor =”Red”
$Button6.ForeColor =”White”
$Button6.Text = “Stop VM”
$Button6.Add_Click({Stop-VM $Name -Force | Display-VMInfo $Name})

# ——– This is the end of the object definition section ——

# —–Draw the empty form—-
$Form = New-Object System.Windows.Forms.Form
$Form.width = 525
$Form.height = 350
$Form.BackColor = “lightblue”
$Form.FormBorderStyle = [System.Windows.Forms.FormBorderStyle]::Fixed3D
$Form.Text = “Hyper-V Virtual Machines”
$Form.maximumsize = New-Object System.Drawing.Size(525,350)
$Form.startposition = “centerscreen”
$Form.KeyPreview = $True
$Form.Add_KeyDown({if ($_.KeyCode -eq “Enter”) {}})
$Form.Add_KeyDown({if ($_.KeyCode -eq “Escape”)
{$Form.Close()}})

#—-Populate the form—-
Display-MainScreen
$Form.Add_Shown({$Form.Activate()})
$Form.ShowDialog()

Conclusion

Throughout this article series, I have demonstrated many different GUI controls that you can use within PowerShell. As this article has demonstrated, you can use these controls to interact with the Windows operating system.