powershell - $string.Substring Index/Length exception

Question

I'm getting this exception when using Substring:

Exception calling "Substring" with "2" argument(s): "Index and length must
refer to a location within the string.
Parameter name: length"
At line:14 char:5
+     $parameter = $string.Substring($string.Length-1, $string ...
+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : ArgumentOutOfRangeException

I understand its meaning, but I'm not sure why I'm getting given the index and length are correct.

I'm doing the following:

$string = "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetserviceshidParameters"
$parameter = $string.Substring($string.Length-1, $string.Length)

Even attempting to hard code it throws the same exception:

$parameter = $string.Substring(68, 69)

Is there something I'm missing?

Answer 1

Your first argument is that starting position in the string, and the second is the length of the substring, starting at that position. The expression for the 2 characters at positions 68 and 69 would be:

$parameter = $string.Substring(68,2)