Powershell event Add_Checked, Add_Unchecked does not occur in custom function

Question

Since I need to create this pattern multiple times in a WPF window, I created a function like below.

function Group_WPF {
    param (
        [Windows.Controls.Canvas]$canvas,
        [int]$top,
        [ref]$f1,
        [string]$n1,
        [ref]$f2,
        [string]$n2,
        [ref]$isR,
        [ref]$isB,
        [ref]$bu,
    )

    $f1.Value = New-Object Windows.Controls.TextBox
    $f1.Value.Width = 380
    [Windows.Controls.Canvas]::SetLeft($f1.Value, 10)
    [Windows.Controls.Canvas]::SetTop($f1.Value, $top + 25)
    $canvas.Children.Add($f1.Value)

    $f1.Value.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $f2.Value = New-Object Windows.Controls.TextBox
    $f2.Value.Width = 380
    [Windows.Controls.Canvas]::SetRight($f2.Value, 10)
    [Windows.Controls.Canvas]::SetTop($f2.Value, $top + 25)
    $canvas.Children.Add($f2.Value)

    $f2.Value.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $isR.Value = New-Object Windows.Controls.CheckBox
    $isR.Value.Content = "Re"
    $isR.Value.IsChecked = $true
    [Windows.Controls.Canvas]::SetLeft($isR.Value, 210)
    [Windows.Controls.Canvas]::SetTop($isR.Value, $top + 50)
    $canvas.Children.Add($isR.Value)

    $isB.Value = New-Object Windows.Controls.CheckBox
    $isB.Value.Content = "Bu"
    [Windows.Controls.Canvas]::SetLeft($isB.Value, 290)
    [Windows.Controls.Canvas]::SetTop($isB.Value, $top + 50)
    $canvas.Children.Add($isB.Value)

    $bu.Value = New-Object Windows.Controls.TextBox
    $bu.Value.Width = 380
    $bu.Value.IsReadOnly = $true
    $bu.Value.Background = [System.Windows.Media.Brushes]::Gainsboro
    [Windows.Controls.Canvas]::SetRight($bu.Value, 10)
    [Windows.Controls.Canvas]::SetTop($bu.Value, $top + 50)
    $canvas.Children.Add($bu.Value)

    $bu.Value.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $isB.Value.Add_Checked({
        $bu.Value.IsReadOnly = $false
        $bu.Value.Background = [System.Windows.Media.Brushes]::White
        $isR.Value.IsChecked = $false
    })

    $isB.Value.Add_Unchecked({
        $bu.Value.IsReadOnly = $true
        $bu.Value.Background = [System.Windows.Media.Brushes]::Gainsboro
    })

    $isR.Value.Add_Checked({
        $isB.Value.IsChecked = $false
    })
}

All works, except the Add_Checked and Add_Unchecked events. When I tried them, I received the following error:

The property 'IsReadOnly' cannot be found on this object. Verify that the property exists and can be set.
At line:111 char:9
+         $bu.Value.IsReadOnly = $false

The property 'Background' cannot be found on this object. Verify that the property exists and can be set.
At line:112 char:9
+         $bu.Value.Background = [System.Windows.Media.Brushes]::White

The property 'IsChecked' cannot be found on this object. Verify that the property exists and can be set.
At line:113 char:9
+         $isR.Value.IsChecked = $false

Please forgive me for my stupidity. Please guide me how to solve this problem. Sincerely thank you.

@MathiasR.Jessen [ref] parameters help me to set many different variable names and use these variables in specific cases. — NqHai
– NqHai, Commented Jun 19, 2024 at 1:56
Use them afterwards? Just output the resulting controls from the function :) — Mathias R. Jessen
– Mathias R. Jessen, Commented Jun 19, 2024 at 8:01

Orace · Accepted Answer · 2024-06-18 15:31:26Z

2

Because you need the local variables from the caller context (ie: $bu, $isR and $isB) you need to call GetNewClosure:

$isB.Value.Add_Checked({
    $bu.Value.IsReadOnly = $false
    $bu.Value.Background = [System.Windows.Media.Brushes]::White
    $isR.Value.IsChecked = $false
}.GetNewClosure())

$isB.Value.Add_Unchecked({
    $bu.Value.IsReadOnly = $true
    $bu.Value.Background = [System.Windows.Media.Brushes]::Gainsboro
}.GetNewClosure())

$isR.Value.Add_Checked({
    $isB.Value.IsChecked = $false
}.GetNewClosure())

I found this solution here.

answered Jun 18, 2024 at 15:31

Orace

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Comments

Mathias R. Jessen · Accepted Answer · 2024-06-19 08:10:39Z

In addition to Orace's suggestion to close over the referenced variables, I'd suggest getting rid of the [ref] parameters - if you want to reference the instantiated controls afterwards simply output them from the function:

function Group_WPF {
    param (
        [Windows.Controls.Canvas]$canvas,
        [int]$top,
        [string]$n1,
        [string]$n2
    )

    $f1 = New-Object Windows.Controls.TextBox
    $f1.Width = 380
    [Windows.Controls.Canvas]::SetLeft($f1, 10)
    [Windows.Controls.Canvas]::SetTop($f1, $top + 25)
    [void]$canvas.Children.Add($f1)

    $f1.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $f2 = New-Object Windows.Controls.TextBox
    $f2.Width = 380
    [Windows.Controls.Canvas]::SetRight($f2, 10)
    [Windows.Controls.Canvas]::SetTop($f2, $top + 25)
    [void]$canvas.Children.Add($f2)

    $f2.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $isR = New-Object Windows.Controls.CheckBox
    $isR.Content = "Re"
    $isR.IsChecked = $true
    [Windows.Controls.Canvas]::SetLeft($isR, 210)
    [Windows.Controls.Canvas]::SetTop($isR, $top + 50)
    [void]$canvas.Children.Add($isR)

    $isB = New-Object Windows.Controls.CheckBox
    $isB.Content = "Bu"
    [Windows.Controls.Canvas]::SetLeft($isB, 290)
    [Windows.Controls.Canvas]::SetTop($isB, $top + 50)
    [void]$canvas.Children.Add($isB)

    $bu = New-Object Windows.Controls.TextBox
    $bu.Width = 380
    $bu.IsReadOnly = $true
    $bu.Background = [System.Windows.Media.Brushes]::Gainsboro
    [Windows.Controls.Canvas]::SetRight($bu, 10)
    [Windows.Controls.Canvas]::SetTop($bu, $top + 50)
    [void]$canvas.Children.Add($bu)

    $bu.Add_MouseDoubleClick({
        param ($source, $e)
        $source.SelectAll()
    })

    $isB.Add_Checked({
        $bu.IsReadOnly = $false
        $bu.Background = [System.Windows.Media.Brushes]::White
        $isR.IsChecked = $false
    })

    $isB.Add_Unchecked({
        $bu.IsReadOnly = $true
        $bu.Background = [System.Windows.Media.Brushes]::Gainsboro
    })

    $isR.Add_Checked({
        $isB.IsChecked = $false
    })

    return [pscustomobject]@{
      F1 = $f1
      F2 = $f2
      IsR = $isR
      IsB = $isB
      BU = $bu
    }
}

Not only does this make the function easier to read, it also becomes much easier to invoke:

$myGroup = Group_WPF -top $top -n1 $n1 -n2 $n2

# now you can reference the individual controls via the properties on the output object:
if ($myGroup.IsB.IsChecked) {
  $myGroup.BU.Text
}

It's so beautiful, I didn't know it was possible to do that. You are so kind and thoughtful, thank you so much.

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