Mongodb c# driver BsonDocument.Parse(stringjson) doesnt convert decimal values with decimal128 type, it takes them as double

Working with Data Drivers
1

The MongoDB.Driver 2.11.x BsonDocument.Parse(stringjson) not converting decimal types in json to decimal128. It always takes it as double.
e.g. json string
{
“bigdecimal”:123456789123456789123456789.23
}

After applying BsonDocument.Parse() the result is as follows:
How can we specify that the certain value is of decimal128 type. Tried the same with BsonSerializer.Deserialize as well, same result.

BsonDocument’s bigdecimal element:

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2

Hello @Shabbir_Lathsaheb, welcome to the MongoDB Community forum!

In MongoDB, by default a number is of type double. That is the reason when you parse the JSON string with a field’s value as a number it is showing as a double. That is the expected behavior. You need to explicitly convert the number to the decimal128 type.

An example, using C# driver API:

var json = "{ 'bigdecimal': 123456789123456789123456789.23 }";
var bson = BsonDocument.Parse(json);
Console.WriteLine(bson.GetValue("bigdecimal").BsonType); // prints Double

// Convert the field to decimal128 type
var decNum = bson.GetValue("bigdecimal").ToDecimal128();
Console.WriteLine(decNum.GetType()); // prints MongoDB.Bson.Decimal128

// Set the element value
bson.Set("bigdecimal", decNum);
3

@Prasad_Saya : Thanks for the reply. However, from the json string we cant know which property is of which type. We don’t have schema defined. Like json parser has ability to accept a setting to consider all float as decimal. Can bson parser not have same user defined settings, since its a conflict?

4

@Shabbir_Lathsaheb, I don’t know of any feature which detects a data type and converts as per your requirement. I think, you may have to build the functionality as per your application needs.

Generally, the MongoDB collection document is mapped to a user defined class in C#. The class can have some functionality to convert to and from the desired data type for specific fields. Applications generally have some structure to their data - that is how various components of the application use the data - from database layer to application layer to user interface layer. These layers have their own ways and methods of data representations and conversions are required, sometimes - as in this case.

Having data without some schema specification is your application and then you need to improvise. I don’t have further suggestions regarding this.

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