Question

Is it a good idea to use MongoDB in .NET desktop application?

Answer 1

Mongo is meant to be run on a server with replication. It isn’t really intended as a database for desktop applications (unless they’re connecting to a database on a central server). There’s a blog post on durability on the MongoDB blog, it’s a common question.

When a write occurs and the write command returns, we can not be 100%
sure that from that moment in time on,
all other processes will see the
updated data only.

In every driver, there should be an option to do a “safe” insert or update, which waits for a database response. I don’t know which driver you’re planning on using (there are a few for .NET, http://github.com/samus/mongodb-csharp is the most officially supported), but the driver doesn’t offer a safe option, you can run the getLastError command to synchronize things manually.

MongoDB won’t make sure your data is on the hard drive immediately. As a
result, you can lose data that you
thought was already written if your
server goes down in the period between
writing and actual storing to the hard
drive.

There is an fsync command, which you can run after every operation if you really want. Again, Mongo goes with the “safety in numbers” philosophy and encourages anyone running in production to have at least one slave for backup.