SQLite in ASP.NET 6.0: Access your database file via HTTP Endpoint

It is one of our fundamental principles to always choose the most-easy-while-capable tool for a job. For this, we try not to shower our customers with the newest, most hip technology available, but to use a technology stack we are

• comfortable with
• quick to provide the required minimum of customer value
• keeping enough options open in order anything changes

One of the heavily affected aspects in that regard is the choice of data storage. There are a lot of different design paradigms one can choose from, but with the “most easy” aspect at hand, the question mostly resolves around the needs of the customer, not the wants (or “might be useful one day”) of the developer.

If your customer already has their PostgreSQL databases distributed in their Kubernetes as an example, it might be advisable to aim for that. If the customer does not have any integrated structure yet, I start with the question:

“Is anything more necessary than a single-file database?“

For one of our ASP.NET 6.0 applications, this was answered with the choice of Sqlite, due to it being native to the Microsoft universe including Entity Framework, which has many common use cases already answered, i.e. gives you way of caring about your application logic more than their database abstractions.

(It might be said that for .NET, an interesting project seems to have been LiteDB, which also operates on a single database file, but at the time of this writing, seems to have gone stale in development / support, and therefore fell out of my favour soon. Sad.).

Now we have a project in which we are closely in touch with the customer and their live system, very often had it been useful to access their platform and take a snapshot of the database for backup or assurance of our logic, and with the technical overhead in that specific case (which required several steps of sequentially granting remote access), I thought myself:

Why can’t I have a (sufficiently secured) HTTP endpoint that gives me this SQLite file as a File download?

The solution was a bit tricky because either the file was not read-accessible during that HTTP request (having been open already), the filestream was not possible because it was being closed too early, or the encoding of the resulting file would not fit. What finally worked was:

        private readonly static System.Text.Encoding enc1252 =
            CodePagesEncodingProvider.Instance.GetEncoding(1252);

        [HttpGet("database")]
        public ActionResult GetDatabase()
        {
            var dataSource = "sqlite.db";
            if (!System.IO.File.Exists(dataSource))
            {
                return NotFound(dataSource);
            }
            db.SaveChanges();
            // Note: CloseConnection() was not required!

            using var fs = new FileStream(dataSource, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            var reader = new StreamReader(fs, enc1252);
            var data = reader.ReadToEnd();
            var ms = new MemoryStream(enc1252.GetBytes(data));
            return new FileStreamResult(ms, "application/octet-stream");
        }

Feel free to comment on that way because I found it more than none-trivial to arrive there, but maybe I missed something obvious. Some definite stumbling stones definitively were in

• The Mime Type “application/octet-stream”, which for some reason would not work with the more adequately sounding choice “application/x-sqlite3” – I have no idea why.
• The Encoding, which on our system was the Windows CodePages-1252 default, which needed to be specified not only in the interpretation of our bytes stream (second location), but also in the definition of the StreamReader itself (first location).
• Please note that if your database is encoded via CP-1252, you also need the System.Text.Encoding.CodePages package (available via NuGet)
• What looks like a missing “using”, is really intentional: If the StreamReader was opened with “using var reader = …”, it had the effect of being disposed before the request was handled correctly – I ran into an error of FileStreamResult: “Cannot access a closed Stream.” – keeping the StreamReader open solved that and the internet told me that this is still not a memory leak; the StreamReader reader gets disposed when the FileStream fs is disposed (see the using in front of that), but it still feels weird.

If you have any comments on that, I’d be very glad to learn from them, but if you don’t and you just have another use case for that problem – I’m happy to help!