Unique filename according to file content

Question

I want to upload files to a web server in a C# project and I already use GUID to get unique filenames. The only problem is that this way I can upload the same file multiple times and always with a different filename.

I would like to find a way to give a file a unique name but always the same, so if I try to upload it again it will have the same filename and I get a message that it already exists.

Any ideas on that?

name them according to the MD5 checksum, or SHA-2 if you're paranoid. — Alex, Jan 14 '16 at 13:22

score 4 · Accepted Answer · answered Jan 14 '16 at 13:23

4

Creating MD5 checksums for your files and using them as filename.

answered Jan 14 '16 at 13:23

1

MD5 checksums should work for this, but aware that there are potential performance issues if the files are large. [This stack overflow question describes][1] how to avoid those issues. [1]: http://stackoverflow.com/questions/1177607/what-is-the-fastest-way-to-create-a-checksum-for-large-files-in-c-sharp – tomRedox Jan 14 '16 at 13:29

score 2 · Answer 2 · answered Jan 14 '16 at 13:28

Use the following code to generate the file name. ComputeHash will generate the hash and GetString will convert the byte array to string.

using (var md5 = MD5.Create())
    {
        using (var stream = new BufferedStream(File.OpenRead(myFile)))
        {
            return string.Concat(md5.ComputeHash(stream));
        }
    }

Unique filename according to file content

2 Answers2