MongoDB C# Driver-Query by List,Cursor,linq 

Retrieving the data from the MongoDB using C# is pretty simple and there are three different ways the data can be rolled out for frontend

List
Cursor
linq 

1.List

data

{
    "_id": { "$oid":"56d5f7eb604eb380b0d8d8ce" },
    "student_id":{ "$numberDouble": "0" },
    "scores":[
        {"type":"exam","score": {"$numberDouble": "78.40446309504266" }},
        {"type":"quiz","score": {"$numberDouble": "73.36224783231339" }},
        {"type":"homework","score": {"$numberDouble": "46.980982486720535" }},
        {"type":"homework","score": {"$numberDouble": "76.67556138656222" }}
    ],
    "class_id":{"$numberDouble": "339"}
}

var documents = collection.Find(new BsonDocument()).ToList();
 foreach(BsonDocument doc in documents)
 {
     Console.WriteLine(doc.ToString());
 }  

//filtering on documents in which inside the scores array there is an exam subdocument with a score value greater than or equal to 95.
var highExamScoreFilter = Builders<BsonDocument>.Filter.ElemMatch<BsonValue>(
"scores", new BsonDocument { { "type", "exam" },
{ "score", new BsonDocument { { "$gte", 95 } } }
});


var highExamScores = collection.Find(highExamScoreFilter).ToList();

2.linq 

 //c#同步变异步的写法
        public virtual async Task<IList<Article>> GetAllArticleAsync()
        {


            var query = _articleRepository.Table;


        //   query = query.OrderByDescending(b => b.CreatedOnUtc);



            var factory = Task<IList<Article>>.Factory;
            var result = await factory.StartNew(() => query.ToList(), System.Threading.CancellationToken.None);

            return result;


        }

3.Cursor

data

{
    "_id": { "$oid":"56d5f7eb604eb380b0d8d8ce" },
    "student_id":{ "$numberDouble": "0" },
    "scores":[
        {"type":"exam","score": {"$numberDouble": "78.40446309504266" }},
        {"type":"quiz","score": {"$numberDouble": "73.36224783231339" }},
        {"type":"homework","score": {"$numberDouble": "46.980982486720535" }},
        {"type":"homework","score": {"$numberDouble": "76.67556138656222" }}
    ],
    "class_id":{"$numberDouble": "339"}
}

filtering on documents in which inside the scores array there is an exam subdocument with a score value greater than or equal to 95.

//filtering on documents in which inside the scores array there is an exam subdocument with a score value greater than or equal to 95.
var highExamScoreFilter = Builders<BsonDocument>.Filter.ElemMatch<BsonValue>(
"scores", new BsonDocument { { "type", "exam" },
{ "score", new BsonDocument { { "$gte", 95 } } }
});


var cursor = collection.Find(highExamScoreFilter).ToCursor();
foreach (var document in cursor.ToEnumerable())
{
     Console.WriteLine(document);
}

using (var cursor = await col.Find(new BsonDocument()).ToCursorAsync())
{
 while (await cursor.MoveNextAsync())
 {
    foreach (var doc in cursor.Current)
    {
        Console.WriteLine(doc);
    }
  }
}

 Referrence http://stackoverflow.com/questions/6772261/retrieve-data-from-mongodb-using-c-sharp-driver.