Update files with MD5 hash in C#

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how to update files with MD5 hash in C#

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how to update files with MD5 hash in C#

Posted 17-Aug-19 2:55am

Member 14013003

Updated 17-Aug-19 19:52pm

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Dave Kreskowiak 17-Aug-19 10:11am

You're going to have to describe what you mean by "update files with MD5 hash". That makes no sense at all on its own.

Richard Deeming 22-Aug-19 10:01am

Once again for those in the cheap seats:

Help us to help you: provide a complete description of the problem, with any relevant parts of your code, and the full details of any errors.

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OriginalGriff · Answer 1 · 2019-08-17T03:48:00

Solution 2

Files don't "have" an MD5 value, it's one of several values you can obtain by passing the file contents as a binary stream through a specific hashing algorithm - in this case the algorithm is MD5
If you change the file content the MD5 (or SHA, or CRC) value will be different - you can't force a file to have a specific MD5 value at all, all you can do is calculate the new value for the new data content.

Posted 17-Aug-19 3:48am

OriginalGriff

Comments

MadMyche 17-Aug-19 11:20am

+5Basically what I was going to write... Except on the second part I was going to add in that Excel would throw a "Circular Reference Error" on this :)

Richard MacCutchan · Answer 2 · 2019-08-17T03:15:00

Solution 1

1. Create an MD5 hash of the file contents: create md5 hash - Google Search[^].
2. Attach the hash data to the file in whichever way you wish.

Posted 17-Aug-19 3:15am

Richard MacCutchan

MadMyche · Answer 3 · 2019-08-17T05:33:00

There are 2 basic methods of doing this

External Reference Method
This is the easiest way to implement
1. Open the file as a memory stream
2. Retrieve the Message Digest
3. Save filename and MD in external file or database

Wrapper/Header Method
This is more complex, and requires a program to parse the files it creates to retrieve and validate.
This is similar to how files are attached to emails.
1. Same
2. Same
3. Create a new memory stream
4. Populate new stream with the MD and the file contents
5. Save new memory stream as new file

RickZeeland · Answer 4 · 2019-08-17T19:53:00

Solution 4

See CodeProject article here: Generating MD5 Hash out of C# Objects[^]
And for a simple answer: c# - Calculate MD5 checksum for a file - Stack Overflow[^]
And also MD5 Class (System.Security.Cryptography) | Microsoft Docs[^]

Posted 17-Aug-19 19:53pm

RickZeeland

Updated 17-Aug-19 20:01pm

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