Expand string without Invoke-Expression

Question

Imagine the following code:

# Script Start
$WelcomeMessage = \"Hello $UserName, today is $($Date.DayOfWeek)\"

..
..
# 100 lines of other functions and what          


        

Answer 1

The canonical way to delay evaluation of expressions/variables in strings is to define them as single-quoted strings and use $ExecutionContext.InvokeCommand.ExpandString() later on.

Demonstration:

PS C:\> $s = '$env:COMPUTERNAME'
PS C:\> $s
$env:COMPUTERNAME
PS C:\> $ExecutionContext.InvokeCommand.ExpandString($s)
FOO

Applied to your sample code:

$WelcomeMessage = 'Hello $UserName, today is $($Date.DayOfWeek)'

...
...
...

function Greet-User {
  $Username = Get-UserNameFromSomewhereFancy
  $Date = Get-DateFromSomewhereFancy

  $ExecutionContext.InvokeCommand.ExpandString($WelcomeMessage)
}