You can not, from inside a Windows 8 application, snap it.
That doesn’t mean there is no other way 🙂
At work, we have to test our app in a snapped state, so we need a way to programmatically make it happen. We discovered that there are two keyboard shortcuts for this action. Windows Key + . (the period key) snaps to the right edge, and Windows Key + Shift + . snaps to the left edge.
So all we have to do is send these keys to the operating system. Sending the Windows Key is tricky, and not supported using only [System.Windows.Forms.SendKeys]::SendWait.
So here’s an alternative:
Download InputSimulator.dll
Run the following commands on a Powershell prompt:
[Reflection.Assembly]::LoadFile("C:\path\to\InputSimulator.dll")
[WindowsInput.InputSimulator]::SimulateModifiedKeyStroke('LWIN', 'OEM_PERIOD')
And your app will snap to the right edge. I am still researching how to snap to the left edge, it’s a more complicated call to SimulateModifiedKeyStroke, but will keep researching.