Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Is GetHashCode for a file unique?

Posted on 2006-07-09
4
727 Views
Last Modified: 2012-05-05
I'm using the following example to get the hash code for a file.  Is this hash code unique or could there be instances of overlapping?  If it's the later (instance of overlapping) help me understand how it occurs or if it's a rarity.

        OpenFileDialog1.FileName = ""
        OpenFileDialog1.ShowDialog()

        If OpenFileDialog1.FileName = "" Then Exit Sub

        Dim File_Stream As New System.IO.StreamReader(OpenFileDialog1.FileName)
        Dim File_Hash As Integer = File_Stream.ReadToEnd().GetHashCode()

        RichTextBox1.Text = File_Hash

        File_Stream.Close()
        File_Stream = Nothing
0
Comment
Question by:IUFITS
  • 2
  • 2
4 Comments
 
LVL 45

Accepted Solution

by:
aikimark earned 500 total points
ID: 17069614
it is a rarity, but collisions can occur.  It only returns a 32-bit value, so there are only 4+ billion unique hash values.

http://msdn2.microsoft.com/en-us/library/system.string.gethashcode.aspx
0
 
LVL 3

Author Comment

by:IUFITS
ID: 17072665
Thanks for the answer.
0
 
LVL 45

Expert Comment

by:aikimark
ID: 17072769
Thanks for the points.  Glad I could help.

A much better hash alternative woulld be SHA-2/SHA160, SHA256, SHA1024.

MD5 is ok for non-sensitive applications, but NIST has put it on a "don't use for criticatl applications" list.
0
 
LVL 3

Author Comment

by:IUFITS
ID: 17072817
Very good, thanks for the additonal info!  :)  I'll keep that in mind.
0

Featured Post

Networking for the Cloud Era

Join Microsoft and Riverbed for a discussion and demonstration of enhancements to SteelConnect:
-One-click orchestration and cloud connectivity in Azure environments
-Tight integration of SD-WAN and WAN optimization capabilities
-Scalability and resiliency equal to a data center

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This tutorial demonstrates one way to create an application that runs without any Forms but still has a GUI presence via an Icon in the System Tray. The magic lies in Inheriting from the ApplicationContext Class and passing that to Application.Ru…
It’s quite interesting for me as I worked with Excel using vb.net for some time. Here are some topics which I know want to share with others whom this might help. First of all if you are working with Excel then you need to Download the Following …
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

856 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question