PowerShell Combobox using a Custom DrawMode

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This post provides an example of creating a pretty PowerShell combobox using a custom DrawMode. Instead of using the default fonts and colours, we can override this setting to conditionally highlight combobox entries in different colours, and even use an alternating background colour.

$form = New-Object System.Windows.Forms.Form
$form.Size = New-Object System.Drawing.Size(450, 180)	
$form.StartPosition = "CenterScreen"
 
$combobox = New-Object System.Windows.Forms.ComboBox
$combobox.Location = New-Object System.Drawing.Point(20, 50)
$combobox.Size = New-Object System.Drawing.Size(390, 20)	
$combobox.DropDownStyle = [System.Windows.Forms.ComboBoxStyle]::DropDownList;
$combobox.FlatStyle = "Flat"
$combobox.BackColor = 'White'
$combobox.Font = "Arial,8pt,style=Bold"
$combobox.Cursor = [System.Windows.Forms.Cursors]::Hand

$combobox.Add_SelectedIndexChanged({
	write-host $combobox.Text $combobox.SelectedValue
})

#must set this to override the draw mode!
$combobox.DrawMode = [System.Windows.Forms.DrawMode]::OwnerDrawFixed

$combobox.Add_DrawItem({
    
 param(
    [System.Object] $sender, 
    [System.Windows.Forms.DrawItemEventArgs] $e
    )
    
    If ($Sender.Items.Count -eq 0) {return}
    
    Try {

        #get current item
        $lbItem=$Sender.Items[$e.Index]
 
        #calculate text colour conditionally
        If ($lbItem -eq "Sample1") {
            $textColor = [System.Drawing.Color]::Red
        }
        ElseIf ($lbItem -eq "Sample2") {
            $textColor = [System.Drawing.Color]::Orange
        }
        ElseIf ($lbItem -eq "Sample3") {
            $textColor = [System.Drawing.Color]::Green
        }
        ElseIf ($lbItem -eq "Sample4") {
            $textColor = [System.Drawing.Color]::Blue
        }
        ElseIf ($lbItem -eq "Sample5") {
            $textColor = [System.Drawing.Color]::Blue
        }
        Else {
            $textColor = [System.Drawing.Color]::Black
        }


        #now calculate background color

        $backgroundColor = if(($e.State -band [System.Windows.Forms.DrawItemState]::Selected) -eq [System.Windows.Forms.DrawItemState]::Selected){ 
             #if item is in focus fill with whitesmoke
             [System.Drawing.Color]::WhiteSmoke
        }else{
            #if item not in focus

            #if we want static background color for all rows
            #[System.Drawing.Color]::White

            #or if we want alternating row colors etc

            if($e.Index % 2 -eq 0){
                [System.Drawing.Color]::White
            }else{
                [System.Drawing.Color]::AntiqueWhite
            }
        }

        #create brushes
        $BackgroundColorBrush = New-Object System.Drawing.SolidBrush($backgroundColor)            
        $TextColourBrush = New-Object System.Drawing.SolidBrush($textColor)
        
        #nice smooth rendering of fonts
        $e.Graphics.TextRenderingHint = 'AntiAlias'
        
        #default font
        $font = $e.Font
        
        #or specify a custom font
        #$font = [System.Drawing.Font]::new($e.Font.FontFamily.Name, 18)
              
        # Draw the background
        $e.Graphics.FillRectangle($BackgroundColorBrush, $e.Bounds)
        
        # Draw the text
        $e.Graphics.DrawString($lbItem, $font, $TextColourBrush, (new-object System.Drawing.PointF($e.Bounds.X, $e.Bounds.Y)))
       
        #we decide not to draw the dotted focus triangle
        #$e.DrawFocusRectangle()
    }
    Catch {
        write-host $_.Exception
    }
    Finally {
        $TextColourBrush.Dispose()
         $BackgroundColorBrush.Dispose()
    }


})

$combobox.items.Add("Sample1") | Out-Null
$combobox.items.Add("Sample2") | Out-Null
$combobox.items.Add("Sample3") | Out-Null
$combobox.items.Add("Sample4") | Out-Null
$combobox.items.Add("Sample5") | Out-Null

$form.Controls.Add($combobox)

[void]$form.showdialog()

Using Powershell to Databind a Combobox with a Value and some Text

Creating a combobox in Powershell and adding an item to it is a relatively trivial task:

$combobox = New-Object System.Windows.Forms.ComboBox
$combobox.Items.add("alkane")

The text of the selected combobox can be obtained like so:

$combobox.Text

This is a combobox in its most simplistic form. The trouble is, I’m from an ASP.Net background and it’s often handy to bind a value (the hidden reference to the selected item – usually a primary key integer) AND some text (the value that the user sees in the combobox – the ‘friendly’ name).  This requires a bit more leg work to implement and can be done by using a datatable, adding data to the datatable, and binding this datatable to our combobox like so:

[void][System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
[void][System.Windows.Forms.Application]::EnableVisualStyles()

#create a form
$form = New-Object System.Windows.Forms.Form

#create a datatable to bind to our combobox
$datatable = New-Object system.Data.DataTable
		
#Define Columns
$col1 = New-Object system.Data.DataColumn "Value",([string])
$col2 = New-Object system.Data.DataColumn "Text",([string])

#add columns to datatable
$datatable.columns.add($col1)
$datatable.columns.add($col2)
		
#Create a row
$datarow1 = $datatable.NewRow()

#Enter data in the row
$datarow1.Value = "Example Value 1"
$datarow1.Text = "Example Text 1"

#Add the row to the datatable
$datatable.Rows.Add($datarow1)

#Create another row
$datarow2 = $datatable.NewRow()

#Enter data in the row
$datarow2.Value = "Example Value 2"
$datarow2.Text = "Example Text 2"

#Add the row to the datatable
$datatable.Rows.Add($datarow2)

#create a combobox
$combobox = New-Object System.Windows.Forms.ComboBox		
$combobox.Add_SelectedIndexChanged({
		#output the selected value and text
		write-host $combobox.SelectedItem["Value"] $combobox.SelectedItem["Text"]
})

#clear combo before we bind it
$combobox.Items.Clear()

#bind combobox to datatable
$combobox.ValueMember = "Value"
$combobox.DisplayMember = "Text"
$combobox.Datasource = $datatable

#add combobox to form
$form.Controls.Add($combobox)	

#show form
[void]$form.showdialog()