Substring is getting too less data - powershell

Question

I want to grab lots of text content from a .sql file between a --Start and --End comment.
Whatever I do somehow I don`t get the substring method correctly to grab only the text within the --Start and --End comment:
text.sql
This text I want not
--Start
this text I want here
--End
This text I want not
This is what I tried:
$insertStartComment = "--Start"
$insertEndComment = "--End"
$content = [IO.File]::ReadAllText("C:\temp\test.sql")
$insertStartPosition = $content.IndexOf($insertStartComment) + $insertStartComment.Length
$insertEndPosition = $content.IndexOf($insertEndComment)
$content1 = $content.Substring($insertStartPosition, $content1.Length - $insertEndPosition)
$content = $content1.Substring(0,$content1.Length - $insertEndPosition)
It would be nice if someone could help me out find my error :-)

Answer 1

There's an attempt to use uninitialized variable in the code:
$content1 = $content.Substring($insertStartPosition, $content1.Length - $insertEndPosition)
The variable $content1 isn't initialized yet, thus the substring call goes haywire. When you run the code again, the variable is set - and results are even more weird.
Use Powershell's Set-StrictMode to enable warnings about uninitialized variables.

Answer 2

It's not the substring approach you are looking for, but I figured that I would toss out a RegEx solution. This will find the text between the --Start and --End on a text file. In this case, I am grouping the matched text with a named capture called LineYouWant and display the matches that it finds. This also works if you have multiple instances of --Start--End blocks in a single file.
$Text = [IO.File]::ReadAllText("C:\users\proxb\desktop\SQL.txt")
[regex]::Matches($Text,'.*--Start\s+(?<LineYouWant>.*)\s+--End.*') | ForEach {
$_.Groups['LineYouWant'].Value
}