Convert GUIDs to a Shorter Textual Representation and Back
The shortest textual representation of a GUID available out-of-the-box is with ToString("N"), which will create a string of 32 characters, e.g.:
b91d07b8826e4233ba40142603cff7ef
If you have several GUIDs next to each other, e.g., in columns in an Excel file, they can take up a considerable amount of space. For my use case (Excel export/import of data from/to an application), hiding the columns was not an option, as I needed to be able to take a look at the GUIDs. Not for the actual value, just to notice differences and patterns in the data.
Behind the scenes, a GUID consists of 128 bits. Converting the bits to a (case-insensitive) hex number as done with ToString("N") leaves some room for improvement. The usual choice for a better conversion from binary to text is base64 encoding, which is described in https://datatracker.ietf.org/doc/html/rfc4648#section-4. This encoding creates text that consists of case-sensitive letters, digits, and only a few special characters (more on that later).
The .NET framework offers the functions Convert.ToBase64String() and
Convert.FromBase64String(), so implementing the conversion is straightforward.
Details worth noting
- The result of
Convert.ToBase64String(someGuid.ToByteArray())is a string that always ends on two padding characters (“==”). These can be removed and added back later for a conversion into the other direction. - The base64 encoding uses the characters “+” and “/”. Depending on your scenario, this may cause issues, so replacing them with different characters is an option. In my case, I did not feel comfortable having arithmetic operators around in Excel, even though they do not cause trouble unless a cell value starts with “=”. This is why my code uses the characters “_” and “$” instead.
The code
I wrote a helper class with two functions and published it on https://github.com/RWeigelt/ShortGuidHelperDemo
The following code
var originalGuid = Guid.NewGuid();
Console.WriteLine($"From GUID : {originalGuid:N}");
var shortId=ShortGuidHelper.GetShortId(originalGuid);
Console.WriteLine($"To short ID : {shortId}");
var recreatedGuid=ShortGuidHelper.GetGuid(shortId);
Console.WriteLine($"Back to GUID: {recreatedGuid:N}");
results in output similar to this:
From GUID : b91d07b8826e4233ba40142603cff7ef To short ID : uAcduW6CM0K6QBQmA8$37w Back to GUID: b91d07b8826e4233ba40142603cff7ef
Ten characters saved for one GUID may not be much, but with several GUIDs next to each other, it still adds up.