Researching the optimal; implementing the practical

Sean Kearny wrote Extending PowerShell to the GUI with Sapien Tools up on Hey, Scripting Guy! Blog. SAPIEN has a product, PrimalForms, which lets you create WinForm applications using PowerShell. One of the advantages using this approach; WinForms is ready out of the box on an end users Windows machine.

In this post I’ll use ShowUI and port Sean’s example. The challenge, ShowUI is a PowerShell Module that needs to be xCopy deployed to the users machine so I can create these WPF GUI applications.

ShowUI

ShowUI is a PowerShell module to help build WPF user interfaces in script. ShowUI makes the complicated world of WPF easy to use in PowerShell.

Sean steps through creating a simple GUI for capturing a user’s first and last name so it can be used with PowerGUI’s Get-QADUser cmdlet. First up, is a simple form with an ‘UNLOCK Account’ button.

Button "Unlock Account" -Show -Margin 10 -On_Loaded {
    $Window.Title = "Our Help Desk"
}

Now, Capture the User Information

I’ll wrap the ShowUI code in a function Get-UserInfo. I like this practice because it makes the GUI widget reusable. In an upcoming post I’ll drill down on how to create custom controls. For now I will reproduce Sean’s user info screen.

I use a WPF Grid which lets me lay out controls in Rows and Columns. I use 3 rows, one row for the labels, one for the text boxes and the last for the button. Every control in ShowUI supports a Row and Column parameter, so they can all be laid out this way.

I write fewer lines of code using a WPF grid container. For example, when I resize the window all the controls resize automatically. Give it a try.

Next up, I show the magic to returning the data entered on the form as PowerShell Hashtable.

function Get-UserInfo {
    Grid -Rows 3 -Columns 2 -Show -On_Loaded {
        $Window.Title = "Our Help Desk"
    } {            

        Label "First Name" -Row 0 -Column 0 -FontWeight Bold
        Label "Last Name" -Row 0 -Column 1 -FontWeight Bold              

        TextBox -Row 1 -Column 0 -Margin 5 -Name FirstName
        TextBox -Row 1 -Column 1 -Margin 5 -Name LastName            

        Button "Unlock Account" -On_Click {
            $Window | Set-UIValue -passThru | Close-Control
        } -IsDefault -Margin 5 -Row 2 -Column 0 -ColumnSpan 2
    }
}            

Get-UserInfo            

# Returns and Prints the hashtable
@"
Name      Value
----      -----
FirstName Mister
LastName  Trouble
"@            

Pressing the button returns a Hash Table

Here is I how I set this up to work. I named the TextBox controls FirstName and LastName. Then in the Button –On_Click event, I pipe the $Window automatic variable to the ShowUI Set-UIValue cmdlet. Set-UIValue takes the content of the TextBox and copies it to the Tag properties. Then, when the form is closed, via Close-Control, the Tag properties are scanned and the name and tag of that control are added to the  hash table as a key value pair.

Variable Splatting

Hashtables (aka associative arrays) are great data structures. Plus, in PowerShell you can use them to do variable splatting.

This is a term taken from the Ruby scripting language and affects how argument variables are passed to commands. – Bruce Payette Windows PowerShell In Action 2nd Edition

To do this is, when referencing the variable that you want to pass to the command, you use @ instead of $ as the prefix to the variable.

Conclusion

So, I can squirrel away my Get-UserInfo function and reuse it. Then, calling the Get-QADUser cmdlet becomes even simpler.

$userInfo = Get-UserInfo
Get-QADUser @userInfo

This approach has another benefit. I can add another TextBox to my GUI, name it the same name as a parameter on Get-QADUser and it will seamlessly work.

These are some of the high order abstractions I and my fellow ShowUI authors, James Brundage and Joel Bennett, are building into ShowUI.

Give it a try and drop us line on CodePlex or our blogs if you have questions or suggestions.

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