This is a real quick one. In PowerShell, the “native” way to express a two-state variable is with Switch parameters.

For instance:

function Test-Thing{ Param([switch]$Recurse) #Code goes here

When calling Test-Thing, you can either supply -Recurse or leave it off. It’s a flag.

This is PowerShell 101.

Programmers coming from other languages are used to Boolean variables. Sometimes, one slips through and makes its way into a parameter list.

It’s not incorrect to have a Boolean parameter. It works just fine, but when I see one it makes me wonder what other PowerShell idioms the writer is not aware of. To me, a Boolean parameter is a code smell.

I mention this because I spotted one in Invoke-SQLCmd this week. [And no, I’m not piling on Invoke-SQLCmd. A co-worker was having problems with Invoke-SQLCmd and asked me to take a look. This was one of the problems]

The -OutputSqlErrors parameter for Invoke-SQLCmd is a Boolean. That means if you want to see SQL errors, you need to pass -OutputSQLErrors $true, rather than just -OutputSQLErrors.

Interestingly enough, there are 8 switch parameters on this cmdlet. This is the only Boolean.

What do you think? Do you ever see parameters like this?

Let me know in the comments.

–Mike