Mastering Windows PowerShell Scripting - Third Edition

The ValidateRange attribute

ValidateRange tests whether a value, or an array of values, fall within a specified range. ValidateRange is most commonly used to test numeric ranges. However, it is also able to test strings. For example, the z string can be said to be within the A to Z range. This approach is slightly harder to apply when testing strings as the Zz string is greater than Z. The following example uses ValidateRange to test an integer value:

function Test-ValidateRange {    [CmdletBinding()]    param (        [ValidateRange(1, 20)]        [Int]$Parameter1    )}