Categories

Reminders via WPF

If I am working on my home machine I don’t necessarily have Outlook or any other application that gives me calendaring capability open. There are times when I need a simple reminder to do something. For some reason I always seem to have PowerShell open so I thought of using the eventing system to give me a reminder.  I could also do this via the task scheduler functions in the PowerShellPack  (Windows 7 Resource kit) which I’ll look at another day.

001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
020
function Set-Alarm {
param (
        [datetime]$time,
       
        [string]$msg = "Alert Issued"
      )     

    $now = Get-Date 
    if ($time -gt $now) {$ts = $time - $now}
    else {throw "Time has to be in future"}
       
    $timer = New-Object -TypeName System.Timers.Timer
    $timer.Interval = $ts.TotalMilliseconds
    $timer.AutoReset = $false
    $timer.Enabled = $true
   
    $global:act = "Start-Process powershell -ArgumentList ""-Sta -WindowStyle Hidden -File C:\Scripts\WPF\show-alert.ps1 """"$msg"""" "" "
   
    Register-ObjectEvent -InputObject $timer -EventName Elapsed -SourceIdentifier TimeAlert  -Action {Invoke-Expression -Command $act }
}

 

My function accepts a time and a message

Set-Alarm "18:47" "Test1"

It then gets the current time, compares the two times and assuming the alert is to be issued in the future creates a Timespan object be subtracting the times as shown.

We can then create  .NET timer object and set the interval to the total number of milliseconds in our timespan. We only want it to fire once so we set autoReset to false and then enable the timer.

I then create a global variable containing the powershell start up commands.  In this case I want it to start in Single Thread mode so I can use the WPF classes.  I call a script when PowerShell starts and pass the script the message.  Note the number of quotes around the $msg variable – this is to make sure the string passed to invoke-expression is correct.  This is messy but needed.

The $act variable has to be global because the action scriptblock for Register-objectevent isn’t evaluated until the event fires.  If $act is in the script scope it won’t be found and the event won’t fire correctly.

 

001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
param (
[string]$msg = "Testing",
[string]$title = "Alert"
)
## load WPF assemblies
Add-Type –assemblyName PresentationFramework
Add-Type –assemblyName PresentationCore
Add-Type –assemblyName WindowsBase

## create a window
$window = New-Object -TypeName System.Windows.Window
$window.Title = $title
$window.Content = $msg
$window.FontSize = 36
$window.SizeToContent = "WidthAndHeight"

## display window
$null = $window.ShowDialog()

 

The script loads the WPF assemblies I need and then creates a window and writes out the message thats been passed in.

This is a bit messy with having to create a global variable but I can’t think of a simpler way to access the variable in the scriptblock for Register-objectevent. The other issue is that I can only have a single event of this type defined because of the variable.  I would need to create the variable with a random name and create another string of the Register-objectevent  invocation.

Technorati Tags: ,,

Leave a Reply