How to create Bson Document with Null value using C# official driver?

Question

I have objects with 3 string fields Country, Province, City. They can contain null or some string name.

I wanna query all data with the exact same values.

Fo

Answer 1

I assume you are working with BsonDocuments and not C# classs. Because of that, for null values, you need to use BsonNull.Value to represent null values in the database and in queries.

Answer 2

Depends on the data type of your city variable. If the city variable is of type BsonValue you can use the ?? operator directly:

BsonValue city = null;
var query = Query.EQ("city", city ?? BsonNull.Value);
Console.WriteLine(query.ToJson());

If your city variable is of type string you need an extra conversion cast to make the compiler happy:

string city = null;
var query = Query.EQ("city", (BsonValue)city ?? BsonNull.Value);
Console.WriteLine(query.ToJson());