Gets the hash of a file, useful for versions of PowerShell before the built in commandlet.

Get-Hash

function Get-Hash {
	param(
		[Parameter(Position=0,Mandatory=$true)]$Path
	)

	# Load crypto library if needed
	if(([AppDomain]::CurrentDomain.GetAssemblies() | ? {$_ -Match 'System.Security'}) -eq $Null) {
		[Reflection.Assembly]::LoadWithPartialName("System.Security") | Out-Null
	}

	$Sha1 = New-Object System.Security.Cryptography.Sha1Managed

	if($Path -ne $Null) {
		$FileHandler = [System.IO.File]::Open($Path, 'open', 'read')
		$Hash = $Sha1.ComputeHash($FileHandler) | % {$_.ToString('x2')}
		$FileHandler.Dispose()

		return (-Join $Hash)
	}