Question

Hi i am trying to create a dynamic form in pwoershell , this is a form which has 5 buttons(color names) and each button opens a different text file(such as if red button is clicked,it should open red.txt; here is the full code;

Script Start

$var = "Red","Blue","Yellow","Black","White"


$testForm = New-Object System.Windows.Forms.Form
$testForm.Text = "Color List"
$testForm.AutoSize = $True
$testForm.AutoSizeMode = "GrowAndShrink"     

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


$Label = New-Object System.Windows.Forms.Label
$Label.Text = "Select the Color"
$Label.AutoSize = $True
$testForm.Controls.Add($Label)


$x=100
$y=50
foreach($color in $var)
{
    $run = New-Object System.Windows.Forms.Button
    $run.Location = New-Object System.Drawing.Size($x,$y)
    $run.Size = New-Object System.Drawing.Size(100,50)
    $run.Text = "$Color"
    $run.Add_Click({ Invoke-Expression "notepad C:\Users\User\$color.txt" })
    $testForm.Controls.Add($run)
    $Font = New-Object System.Drawing.Font("Times New Roman",14,[System.Drawing.FontStyle]::Regular)
    $run.font = $Font
    $run.AutoSize = $True
    $y+=50

}
$testForm.ShowDialog()

END Script

Everything went fine until, when the form opens with buttons, and all the buttons when clicked, open the file “White.txt” since its the last element in the array; is there any way to change the script to make each button open only their respective files and not the last color file?

please do let me know if any further questions or clarifications needed.

Answer 1

Looks like the problem is the Add_Click line. The script block contains a link to the variable $color, rather than evaluating it immediately to create a new “notepad…” string for Invoke-Expression and linking to that. The string for Invoke-Expression will be created when the button is clicked. By this time $color is White ‘cos the loop has finished, so all the buttons end up creating a string using White.

You can fix it with a call to GetNewClosure() which will build cause the string for the Invoke-Expression to be created during the loop, not later on when the button is clicked. So change the line to:

$run.Add_Click({ Invoke-Expression "notepad C:\Users\User\$color.txt" }.GetNewClosure())

And it should work as expected.