using System;

using MongoDB.Bson;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string input = @"{

            ""CRM"" : {

                ""Teste"" : ""true""

            },

            ""Endereco"" : {

                ""Cidade"" : ""MARINGA""

            },

            ""Vendas"" : [

                    {

                        ""idP"" : NumberInt(34),

                        ""txt"" : ""001""

                    },{

                        ""idP"" : NumberInt(34),

                        ""txt"" : ""002""

                    }

            ],

            ""Tipos"" : [

                    {

                        ""idT"" : NumberInt(34),

                        ""idTipo"" : NumberInt(34)

                    },{

                        ""idT"" : NumberInt(34),

                        ""idTipo"" : NumberInt(34)

                    }

            ]

        }";

        BsonDocument bson = BsonDocument.Parse(input);

        Console.WriteLine(String.Join(",", GetRootDocumentAllKeys(bson)));

    }

    private static List<string> GetRootDocumentAllKeys(BsonDocument bson)

    {

        List<string> collectionKeys = new List<string>();

        collectionKeys.AddRange(GetDocumentKeys(bson));

​

        return collectionKeys.Distinct()

            .ToList();

    }

    private static List<string> GetDocumentKeys(BsonValue value)

    {

        List<string> keys = new List<string>();

​

        if (value == null)

            return keys;

​

        if (value.GetType() != typeof(BsonDocument))

            return keys;

​

        foreach (var kvp in (BsonDocument)value)

        {

            keys.Add(kvp.Name);

​

            keys.AddRange(GetArrayKeys(kvp.Value));

            keys.AddRange(GetDocumentKeys(kvp.Value));

        }

​

        return keys;

    }

​

    private static List<string> GetArrayKeys(BsonValue value)

    {

        List<string> keys = new List<string>();

​

        if (value == null)

            return keys;

​

        if (value.GetType() != typeof(BsonArray))

            return keys;

​

        foreach (var item in (BsonArray)value)

        {

            keys.AddRange(GetArrayKeys(item));

            keys.AddRange(GetDocumentKeys(item));

        }

​

        return keys;

    }

}