A fundamental best practice for any programming or scripting language is do not trust your input parameters, always validate data users (but also other pieces of automation) pass into your program. It is easy it imagine how things can go badly wrong when a user by mistake passes a string where you are expecting an integer, or an array in place of a boolean, not to mention the security implications (and potential disaster) of, for example, accepting and running things such as a sql command or other shell commands malicious users may try to use to exploit your system. In Powershell we can use Parameter Validation attributes to check the format or the type of an input parameter, or check for null or empty strings, or that the passed value falls within a certain range, or force the user to pass only a value selected from a restricted list. This last type is called ValildateSet and allows the script author to decide the list of values the user can chose from and have Powershell throws an error if this constraint is not respected. I used it often in my scripts and modules, this is how a very simple script looks like: [CmdletBinding()]param (…
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