Projection from Mongo API C# driver not supported while querying DocumentDB - azure-cosmosdb

Question

I am using following code (MongoDB C# driver) to projects fields ,
where queryDocument = '{{ "FullName" : /myname/i }}'
BsonDocument projectionDefination = Builders.Projection.ToBsonDocument();
projectionDefination.Add(new BsonElement("FullName", "myname"));
collection.Find(queryDocument).Project(projectionDefination);
getting following error:
{"Command failed."}
{{ "_t" : "OKMongoResponse", "ok" : 0, "code" : 9, "errmsg" : "Syntax error, incorrect syntax near '9'.", "$err" : "Syntax error, incorrect syntax near '9'." }}
Can anyone update on this?
I also tried above with RoboMongo
Command: db.getCollection('Employee').find({ "FullName": /User/i}).projection({ "FullName" : "$FullName" })
Received following error:
Error: error: {
"_t" : "OKMongoResponse",
"ok" : 0,
"code" : 9,
"errmsg" : "Syntax error, incorrect syntax near '15'.",
"$err" : "Syntax error, incorrect syntax near '15'."
}

Answer 1

According to your description, I checked this issue and I could encounter the same issue:
As mongoDB document states about Projection in db.collection.find():
The projection parameter determines which fields are returned in the matching documents. The projection parameter takes a document of the following form:
{ field1: <value>, field2: <value> ... }
The <value> can be any of the following:
1 or true to include the field in the return documents.
0 or false to exclude the field.