Case-insensitive PowerShell replacement - powershell

Question

I have the following PowerShell script:
$RegExplorer = Get-ItemProperty -Path HKLM:\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
$NullSessionPipes = "$($RegExplorer.NullSessionPipes)"
$NullSessionPipes
$NullSessionPipes = $NullSessionPipes.replace("browser", "")
$NullSessionPipes
The script works fine as long as the registry key examining exactly matches the case I've specified - "browser".
However if the case was different in the registry key say "BROWSER" or "Browser" it doesn't do the replacement.
I'm looking for some way to make string.replace case insensitive. I know I could convert the string using .tolower or .toupper first to make comparison easier, but I don't know if this particular registry key or applications which access it are case sensitive, so I don't want to change the case of existing key.
Is there an easy way to do this?

Answer 1

Call me pedantic but while nobody here was outright wrong, nobody provided the correct code for the final solution either.
You need to change this line:
$NullSessionPipes = $NullSessionPipes.replace("browser", "")
to this:
$NullSessionPipes = $NullSessionPipes -ireplace [regex]::Escape("browser"), ""
The strange [regex] text isn't strictly necessary as long as there are no regular expression characters (ex. *+[](), etc) in your string. But you're safer with it. This syntax works with variables too:
$NullSessionPipes = $NullSessionPipes -ireplace [regex]::Escape($stringToReplace), $stringToReplaceItWith

Answer 2

NullSessionPipes is a multi-string value and the replace method (in addition of being case-sensitive) may fail if there's more than one string in it. You can use the -replace operator. By default, all comparison operators are case-insensitive. Case-sensitive operators starts with 'c', like: -creplace,-ceq, etc.
Operators that starts with 'i' are case-insensitive, like -ireplace,-ieq, and they are the same as -replace, -ieq.
See the about_Comparison_Operators for more information.

Answer 3

Use a regular expression replacement instead:
$RegExplorer = Get-ItemProperty -Path HKLM:\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
$NullSessionPipes = "$($RegExplorer.NullSessionPipes)"
$NullSessionPipes
$NullSessionPipes = $NullSessionPipes -replace "browser", ""
$NullSessionPipes

Answer 4

The .Replace method doesn't have a case-insensitive option:
String.Replace method
...This method performs an ordinal (case-sensitive and culture-insensitive) search...
https://msdn.microsoft.com/en-us/library/fk49wtc1(v=vs.110).aspx
The other answers to this question suggest using -replace or -ireplace, which is fine if you want to use regex replacement. However, as #Bob mentions in his (her?) comments this isn't always appropriate. An example might be if you want to include a literal string such as $_ in the replacement text.
One trick borrowed from other case-sensitive places is to convert the "input" string and the "search" string to lower case:
[PS]> "TeXT".ToLower().Replace("text","NewString")
NewString
However... this causes the output to be in lower case for anything that doesn't match the search string, which may well be unacceptable.
[PS]> "DON'T CHANGE MY TeXT".ToLower().Replace("text","NewString")
don't change my NewString

Answer 5

The String.Replace method has two different overloads that allows a case-insensitive replacement:
Replace(String, String, StringComparison)
Replace(String, String, Boolean, CultureInfo)
For the first one, you need to pick a StringComparison that ignores case, e.g. OrdinalIgnoreCase.
For the second one, it's the Boolean that controls case sensitivity; a null for the CultureInfo uses the current culture.
Using these in PowerShell 7 would look like:
$s = 'All the HIP cats'
$s.Replace('hip','cool') # doesn't work: All the HIP cats
$s.Replace('hip','cool','OrdinalIgnoreCase') # works : All the cool cats
$s.Replace('hip','cool',$true,$null) # works : All the cool cats