Replace Database connection string using PowerShell - sql-server

Question

I am working on a script that should display the current database a program is connected to, and also give an option to replace with a new database (either by manually entering the database name but preferably listing all databases on the local server \ instance and give users "number selection" to select the database they want to use.
The connection string is saved in a text file called server.exe.config below is an example of what the file contains, its not the only data in the config file obviously
<add key="persistency.connection" value="data source=MyDatabaseServer;initial catalog=MyDatabase1;Integrated Security=True" />
I can use Get-Content to see the entire file and also use Where-Object {$_ -like "*initial catalog=*"} to see the only line which has the database configuration.
But I think this will be difficult for users to interpret what database is being used so if possible need a command that will display just the database name that is in the config file instead of the entire line, save that database name for future replacement when the user selects a new database to be replaced into the config file.
Possible?

Answer 1

While plain-text processing, as shown in your own answer, works in simple cases, for robustness it is usually preferable to use XML parsing, such as via the Select-Xml cmdlet:
$file = './server.exe.config'
# Extract the XML element of interest, using an XPath query
$xpathQuery = '/configuration/appSettings/add[#key = "persistency.connection"]'
$el = (Select-Xml $xpathQuery $file).Node
# Replace the database name in the element's value...
$newDatabase = 'NewDatabase'
$el.value = $el.value -replace '(?<=\binitial catalog=)[^;]+', $newDatabase
# ... and save the modified document back to the file.
# IMPORTANT: Be sure to use a *full* path to the output file,
# because PowerShell's current directory (location)
# usually differs from .NET's; Convert-Path ensures that.
$el.OwnerDocument.Save((Convert-Path $file))
Note that this technique works in principle for any XML file, not just .config.exe files.

Answer 2

I think this is simpler and works for me
$ConnString = Get-Content -Path $filepath\server.exe.Config | Where-Object {$_ -like "*initial catalog=*"}
$ConnString -split '\s*;\s*' | ForEach-Object -Process {
if ($_ -imatch '^initial catalog=(?<dbname>.+)$') {
$ConnStringdb = $Matches.dbname
}
}
I am then using the following simply to replace the text above back into the config file after a database name is enter - Manually. would love if I could get it to work automatically by maybe building an array or something.
Write-Host "Please Enter the database name you want to use for Production(Don't Leave Blank): " -NoNewline; $NewDatabaseConfig = Read-Host;
(Get-Content -Path $filepath\server.exe.Config -Raw) -Replace $ConnStringdb,$NewDatabaseConfig | Set-Content -Path $IPSServerProd\UBERbaseOfficeServer.exe.Config