Question

Anybody here can help me with this

Input file

  Type Reference      
   WIN  00001  
   WIN  00001   
   WIN  00001  
   MAC  00001  
   MAC  00001  

Basically I need to compare if the first 3 character that are not equal

preferred output will be

Type Reference

   WIN  00001  
   WIN  00001   
   WIN  00001  

Code below

Dim fh As StreamReader
Dim os as string
fh = new StreamReader("haggis.txt")
Dim s As String = fh.ReadLine()
While not s Is Nothing
   os = s.Substring(0,3) 
   if os <> os then
      Console.WriteLine("Write here")
   else

   end if    

   s = fh.ReadLine
End While
fh.Close()
End Sub

Answer 1

Declare a previousOS variable, and compare it with that.

e.g.

Dim fh As StreamReader
Dim previousOS as string REM to see what previous os was
Dim os as string
fh = new StreamReader("haggis.txt")
Dim s As String = fh.ReadLine()
While not s Is Nothing
  previousOS = os 
  REM save the old os in this variable before assigning it to a new variable
  os = s.Substring(0,3) 
REM check if the new os is equal to the previousOS string (null check if it the first time read
if previousOS <> Nothing AndAlso previousOS <> os then
   Console.WriteLine("Write here")
else

end if    

s = fh.ReadLine
End While
fh.Close()
End Sub