Using regular expression from Powershell in C#

I have a Powershell script that will parse the content of a txt file, and use regular expression to get rid of things not needed.

My issue is that I would like to convert the small script to be in C#. I am having some issues with how regex works in C# and what my limitations are.

Here is the script:

$x = (Get-Location).Path + "\MasterFile.txt"

$file = Get-ChildItem "$x"
$pathOfx = $file.DirectoryName

$dataExtractedFolder = "$pathOfx\TestFolder"
New-Item -Path $dataExtractedFolder -ItemType directory -Value $_ -Force 


[string](cat "$x") | Foreach-Object {$_ -replace "\(in\)", ""} | Set-Content -path "$dataExtractedFolder\Master Trace Data.txt"

#This will extract only the data in the selected Master File that starts with a "12 43" and ends with "12 44"
$src = [IO.File]::ReadAllText("$dataExtractedFolder\Master Trace Data.txt")
$pattern ='(?<Key>(TEMP\s*:\s*12\s*4[34]))\s*(?<Num>(\b[0-9A-F]{2}\s+)+)'
[Regex]::Matches($src, $pattern) | % { [Regex]::Replace($_.Groups['Key'].Value, 'TEMP\s:\s*', '') + ' ' + [Regex]::Replace($_.Groups['Num'].Value, '\s+', ' ') }|set-content "$dataExtractedFolder\Master Trace Data.txt" 

The file I am parsing has a lot of items I do not need. The script will also strip the file of "(in)" and replace it with an empty string.  I am only looking for a particular group of text blocks but can I use the same regular expression as the $pattern in C# doing something like this:

System.Text.RegularExpressions.Regex g = new System.Text.RegularExpressions.Regex(@"(?<Key>(TEMP\s*:\s*12\s*E[34]))\s*(?<Num>(\b[0-9A-F]{2}\s+)+)");

Then Can I parse my data each line by line using the System.Text.RegularExpressions.Regex.IsMatch(s, sPattern);

I would basically like to convert the script to C# but I am lost on how.

Kind Regards