Mongodb C# driver ignore Null and Empty Lists (ToBsonDocument)

Question

ConventionRegistry.Register("IgnoreIfDefault", 
                            new ConventionPack { new IgnoreIfDefaultConvention(true) }, 
                            _ => true);

var bsonDocument = anon.ToBsonDocument();

using IgnoreIfDefaultConvention can cause an unintended behavior due to the fact it affects all default values. For instance, values, as listed below, will not be saved:

int = 0
decimal = 0
bool = false

If I want to ignore only null values and Empty Arrays what is the best approach?

dododo · Accepted Answer · 2021-07-16 08:18:35Z

2

I didn't use it my own, but I think the answer is this convention: IgnoreIfNullConvention. Also you may configure a particular convention for a particular field:

BsonClassMap.RegisterClassMap<test>(c => c.MapField(e => e.A).SetIgnoreIfNull(ignoreIfNull: true));

or use this attribute BsonIgnoreIfNullAttribute

UPDATE: If you need more complicated convention, you can always implement a custom one: https://mongodb.github.io/mongo-csharp-driver/2.12/reference/bson/mapping/conventions/

edited Jul 16, 2021 at 8:18

answered Jul 15, 2021 at 17:31

dododo

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4 Comments

AliReza Sabouri Over a year ago

thanks for the reply. I don't have a separate class and that's why I can not use attributes and RegisterClassMap. the goal is to convert dynamic or anonymous objects to BsonDocument also exclude null and empty lists.

AliReza Sabouri Over a year ago

IgnoreIfNullConvention doesn't ignore empty lists

dododo Over a year ago

doesn't ignore empty lists because it's not null? If you need more complicated convention, you can always implement a custom one: mongodb.github.io/mongo-csharp-driver/2.12/reference/bson/…

AliReza Sabouri Over a year ago

looks like this is what I need Custom Conventions. I'll try to write my own custom convention. just update your answer like your last comment (if you want) I will accept that. if not I will post the custom convention later. thanks

Daniele Bosa · Accepted Answer · 2024-08-14 11:31:20Z

0

This is the custom attribute we use to ignore empty collections:

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field)]
public class BsonIgnoreIfEmpty : Attribute, IBsonMemberMapAttribute
{
    public void Apply(BsonMemberMap memberMap)
    {
        // Get the member where the attribute is applied
        MemberInfo memberInfo = memberMap.MemberInfo;

        memberMap.SetShouldSerializeMethod(entity =>
        {
            // Get value of memberInfo
            var member = memberInfo switch
            {
                FieldInfo field => field.GetValue(entity),
                PropertyInfo property => property.GetValue(entity),
                _ => null
            };

            if (member is IEnumerable collection)
            {
                // Check if collection is empty
                return collection.GetEnumerator().MoveNext();
            }

            return false;
        });
    }
}

answered Aug 14, 2024 at 11:31

Daniele Bosa

1

1 Comment

Community Over a year ago

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