Extracting Directory String from Text - vb.net

Question

I have a program that I am making with visual basic 2010 that will pull logs of corrupted files and give the user the location of the corrupted file(s) to fix it. These logs are huge and vary depending on the amount of corruption.
I already have set in code to only pull the lines of text that are flagged as errors but, within these lines, there are directories that point to what file is corrupted. I need to know if there is any way to read these directories and put them into a RichTextBox. Here is an example of a line from a log file:
oa = #0x238282b270->OBJECT_ATTRIBUTES {s:48; rd:NULL; on:[100]"\??\C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f"; a:(OBJ_CASE_INSENSITIVE)}, iosb = #0x238282b250, as = (null), fa = 0,
And here is the part that I need to pull from it:
C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f from this string
I'm pretty new to all of this, so bear with me please.

Answer 1

RegEx provides great flexibility for this sort of thing, but you need to establish a known pattern that defines where the path begins and ends. For instance, if it always is prefixed by on:[100]"\??\ and always ends with ";, then you could extract it with this RegEx pattern:
on:[100]"\\?\?\(.*?)";
Here's what the pattern means:
on:\[100\]"\\\?\?\\ - Matches must begin with on:[100]"\??\ exactly
The extra backslashes are necessary to escape all of the special characters which would otherwise have special meaning. In this case, [, ], \, and ? all have special meaning to RegEx, so they each need to be preceded a the backslash to escape them.
(.*?) - Matches can contain any number of any characters between the preceding on:[100]"\??\ and the following ";. The value of this portion of the input is captured as an unnamed group (i.e. group 1).
( - Begins a capturing group
. - Matches any character
* - Any number of times
? - Matches in a non-greedy fashion (i.e. only captures up through the first instance of whatever follows it in the pattern)
) - Ends the capturing group
"; - Matches must end with these two characters exactly
So, for instance:
Dim input As String = "oa = #0x238282b270->OBJECT_ATTRIBUTES {s:48; rd:NULL; on:[100]""\??\C:\Windows\WinSxS\amd64_3ware.inf.resources_31bf3856ad364e35_10.0.10130.0_en-us_ca9e7cc7a071e60f""; a:(OBJ_CASE_INSENSITIVE)}, iosb = #0x238282b250, as = (null), fa = 0,"
Dim m As Match = Regex.Match(input, "on:\[100\]""\\\?\?\\(.*?)"";")
If m.Success Then
Dim path As String = m.Groups(1).Value
End If
Or, if the input can contain multiple matches, you can loop through them like this:
For Each m As Match In Regex.Matches(input, "on:\[100\]""\\\?\?\\(.*?)"";")
Dim path As String = m.Groups(1).Value
Next
That's just an example. Depending upon your needs, you could adjust the RegEx pattern as necessary. RegEx is very flexible, so as long as there's some logical way to recognize where the path is in the string, it should be possible to find it with a RegEx pattern. On a side note, since the pattern is, itself, just a string, it can be stored in a configuration setting outside of the code too, which is an added benefit.