Unrecognized escape sequence \P while parsing the data using powershell - powershell

Question

I am using below properties and powershell script to parse the data from properties file. But it is failing while trying to read backslash character "\" in the datasource string. I tried to fix it by adding additional backslash in the properties file. But I am looking for the solution to handle it in powershell instead of making any changes in the properties file.
#env.properties value
datasource=SERVER.SUBDOMAIN.SUBDOMAIN2.DOMAIN.TLD\PWDFC1;initialcatalog=SAA;Trusted_Connection=True;MultiSubnetFailover=True
#Powershell Script
$EnvProps='C:\Apps\SAA\config\env.properties'
$AppConfig= 'C:\Apps\SAA\config\app.config'
$ReadProps = convertfrom-stringdata ([IO.File]::ReadAllText($EnvProps))
foreach($key in $ReadProps.Keys)
{
$value = $ReadProps[$key]
(Get-Content $AppConfig) -replace "##$key##", $value | Set-Content $AppConfig
}
Error while running above script
INFO 2021-08-30 14:22:37 Executing command ...
INFO 2021-08-30 14:22:37
ERROR 2021-08-30 14:22:53 convertfrom-stringdata : parsing "data
source=SERVER.SUBDOMAIN.SUBDOMAIN2.DOMAIN.TLD\PWDFC1;initial
ERROR 2021-08-30 14:22:53 catalog=SAA;Trusted_Connection=True;MultiSubnetFailover=True" -
Unrecognized escape sequence \P.

Answer 1

You need to escape backslashes in the data string. Per the documentation:
ConvertFrom-StringData supports escape character sequences that are allowed by conventional machine translation tools.... the cmdlet can interpret backslashes (\) as escape characters.... instead of the PowerShell backtick character (`) that would normally signal the end of a line in a script. Inside the here-string, the backtick character does not work.
Further mentioned in the link above, it supports escape sequences which are used by regular expressions. You can escape your string prior to putting it through ConvertFrom-StringData by using the [regex]::Escape(string) static method. This will automatically escape any expression tokens in your data so they are parsed literally.
You also need separate each key and value so they fit on their own line, though this is something you will run into once you resolve the error above. Alternatively, you can split on the semi-colon ; prior to running the string through ConvertFrom-StringData. This is also mentioned in the cmdlet documentation.
In the end, the data string you pass to ConvertFrom-StringData should look like this:
datasource=SERVER.SUBDOMAIN.SUBDOMAIN2.DOMAIN.TLD\\PWDFC1
initialcatalog=SAA
Trusted_Connection=True
MultiSubnetFailover=True
Edit
I missed this on the first go, but you also need to remove the semi-colons ; from the string before using ConvertFrom-StringData. This won't cause any errors, but the ; will be included as part of the value, which is likely undesirable. I have updated the sample data above to reflect this.