mongodb c# how to work with BSON document

Question

I've spent MANY hours looking for the answer... This is very easy in PHP but I just can't put it together in C#(I'm new to C# and mongo...) I'm trying to iterate through all levels of a stored document. The document looks like this:

{     "_id": ObjectId("51f90101853bd88971ecdf27"),     "fields": [         {             "ID": ObjectId("51fd09498b080ee40c00514e"),             "NAME": "ID",             "TYPE": "Text"         },         {             "ID": ObjectId("51fd09a68b080ee40c0064db"),             "NAME": "Title",             "TYPE": "Text"         },         {             "ID": ObjectId("51fd09b28b080ee40c004d31"),             "NAME": "Start Date",             "TYPE": "Date"         },         {             "ID": ObjectId("51fd09c28b080ee40c007f2e"),             "NAME": "Long Description",             "TYPE": "Memo"         }     ],     "name": "TODB",     "updated": "Wed Jul 31 2013 08:20:17 GMT-0400 (Eastern Daylight Time)" } 

I have no problem accessing the "name" and "updated" but can't figure out how to access the "fields" array.

Code so far :

{     MongoServer mongo = MongoServer.Create();     mongo.Connect();     var db = mongo.GetDatabase("forms");      mongo.RequestStart(db);     var collection = db.GetCollection("forms");     var query = new QueryDocument("name",     "TODB");      mongo.Disconnect(); }  @foreach(BsonDocument item in collection.Find(query)) {     @item.GetElement("name").Value     @item.GetElement("_id").Value } 

Again, I am able to access the name and _id just not any of the sub document values.

Thanks in advance for any assistance! After I get the reading figured out, I am also going to want to write data....

Answer 1

There are a few ways, but here's one:

 // build some test data  BsonArray dataFields = new BsonArray { new BsonDocument {       { "ID" , ObjectId.GenerateNewId()}, { "NAME", "ID"}, {"TYPE", "Text"} } };  BsonDocument nested = new BsonDocument {      { "name", "John Doe" },      { "fields", dataFields },      { "address", new BsonDocument {              { "street", "123 Main St." },              { "city", "Madison" },              { "state", "WI" },              { "zip", 53711}          }      }  };  // grab the address from the document,  // subdocs as a BsonDocument  var address = nested["address"].AsBsonDocument;  Console.WriteLine(address["city"].AsString);   // or, jump straight to the value ...  Console.WriteLine(nested["address"]["city"].AsString);  // loop through the fields array  var allFields = nested["fields"].AsBsonArray ;  foreach (var fields in allFields)  {      // grab a few of the fields:      Console.WriteLine("Name: {0}, Type: {1}",           fields["NAME"].AsString, fields["TYPE"].AsString);  } 

You can often use the string indexer ["name-of-property"] to walk through the fields and sub document fields. Then, using the AsXYZ properties to cast the field value to a particular type as shown above.