MongoDB C# - Getting BsonDocument for an Element that doesn't exist

Question

So I have a BsonDocument b (let's say it has FirstName, LastName, Age), which you could access as b["FirstName"], etc...

If I try to do b["asdfasdf"] (which doesn't exist of course), instead of returning null, it errors out the app. What's the correct way to check? Do I really have to do a try/catch?

Answer 1

There is also an overload that lets you provide a default value:

BsonDocument document;
var firstName = (string) document["FirstName", null];
// or
var firstName = (string) document["FirstName", "N/A"];

which is slightly more convenient that using Contains when all you want to do is replace a missing value with a default value.

Edit: since the 2.0.1 version, it has been deprecated in favor of GetValue:

var firstName = document.GetValue("FirstName", new BsonString(string.Empty)).AsString;