mongodb c# client problem with $or query with the same operator

In MongoDb Compass I can query a collection like the following:
{ age: { $eq: "65", $eq: 65} }

As you might ask - I don't know if age is a string or number.
How can I make such a query in c#?
I tried a IEnumerable<KeyValuePair<string, object>> and give this to a BsonDocument - but I get an error with duplicate keys which is obvious cause there are two $eq operators.
But how to do it right in c#?

var para = comparisonOperator.Parameter.Name;
var op = FilterComparisonOperators.GetComparisonMongoDbOperator(comparisonOperator.Name);
var value = comparisonOperator.Value.Name;
if (int.TryParse(value, out int intValue))
{
    var bsonDocument = new BsonDocument(op, intValue);
    filterDocument.AddRange(new BsonDocument(para, bsonDocument));
    filterDocument.AddRange(new BsonDocument(para, bsonDocument));
}
else
{
    var bsonDocument = new BsonDocument(op, value);
    filterDocument.AddRange(new BsonDocument(para, bsonDocument));
}

I want to query a number like 65 as number or string.

You can use $or like this query or $in like this other query so you can try something like this in Linq way:

Using $or (||)

var result = collection
               .AsQueryable<YourClass>()
               .Where(x => x.Age == 65 || x.Age == "65")
               .ToList();

Using $in (.In())

var result = collection
               .AsQueryable<YourClass>()
               .Where(x => x.age.In(new[] { 65, "65" }))
               .ToList();

Or something like this (according to this question)

Using $or:

var builder = Builders<BsonDocument>.Filter;
var filter = builder.Eq("age", 65) | builder.Eq("age", "65");
db.collection.Find(filter).ToList();

Using $in:

var builder = Builders<BsonDocument>.Filter;
var filter = builder.In("age", new object[] { 65, "65" });
db.collection.Find(filter).ToList();