Search A String Buffer With Nulls (chr(0))?

I need to search a buffer for a string of characters.The buffer is essentially a binary file (it's an image) and contains lots of chr(0) characters.The string I need to locate also contains chr(0) characters. In fact it is the following string:

chr(100) & chr(0) & chr(0) & chr(163)

This is a marker in the image file for items I need to process.So I though I would do the following:

Dim sFileBuffer as String = system.io.file.readalltext("myimagefile")
Dim sLookFor as String = chr(100) & chr(0) & chr(0) & chr(163)
Dim iLocation as Integer = sFileBuffer.IndexOf(sLookFor)

The problem is that, although the characters in sLookFor definitely exist inside of sFileBuffer - IndexOf will always return -1 (not found).I tried the following:

Dim Marker() as Byte = {100, 0, 0 , 163}
Dim sLookFor as String = System.Text.Encoding.UTF8.GetString(Marker)
Dim sFileBuffer as String = system.io.file.readalltext("myimagefile", Encoding.UTF8)
Dim iLocation as Integer = sFileBuffer.IndexOf(sLookFor)

But this appears to only find occurrences of Chr(100) & Chr(0) - not the full 4 character sequence I desire. It appears to see the second Chr(0) as a termination of the search string.I think the sticking point here is the null. Yes - I can string.replace(chr(0), Chr(255)) in both the sLookFor and the sFileBuffer and adjust my search accordingly - but that seems like a mess to me.Is there not a way to search a buffer of binary data? I've tried working with byte arrays - but there appears to be no way to easily search for a sequence of byte values - just individual elements in the array.