The Find and FindAsync methods are used to to retrieve data from a collection in MongoDB and all queries in MongoDB have the scope of a single collection.

Follow the Install and Connect to MongoDB step to connect to a running MongoDB instance.

The below code will finds documents whose Name field equals “Himen”.

 using System;  
 using System.Threading.Tasks;  
 using MongoDB.Bson;  
 using MongoDB.Driver;  
 namespace MongoDB  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       FindDoc(args).Wait();  
       Console.WriteLine("Press Enter");  
       Console.ReadLine();  
     }  
     static async Task FindDoc(string[] args)  
     {  
       var _connectionString = "mongodb://localhost:27017";  
       var _client = new MongoClient(_connectionString);  
       var _database = _client.GetDatabase("blog");  
       var _collection = _database.GetCollection("users");  
       var _list = await _collection.Find("{Name : 'Test user'}").ToListAsync();  
       foreach(var _doc in _list)  
       {  
         Console.WriteLine(_doc);  
       }  
     }  
   }  
 }  

The InsertOneAsync method and the InsertManyAsync method are used to add documents to a collection in MongoDB. If documents to a collection that does not exist, MongoDB will create the collection.

We can use InsertManyAsync while inserting more than one document.

Follow the Install and Connect to MongoDB step to connect to a running MongoDB instance.

 using System;  
 using System.Threading.Tasks;  
 using MongoDB.Bson;  
 using MongoDB.Driver;  
 namespace MongoDB  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       InsertDoc(args).Wait();  
       Console.WriteLine("Press Enter");  
       Console.ReadLine();  
     }  
     static async Task InsertDoc(string[] args)  
     {  
       var _connectionString = "mongodb://localhost:27017";  
       var _client = new MongoClient(_connectionString);  
       var _database = _client.GetDatabase("blog");  
       var _collection = _database.GetCollection("users");  
       var _document = new BsonDocument   
        {   
         { "Name", "test user" },   
         { "Email", "test@xxx.com" },   
         { "Address1", "5619 other st" },   
         { "City", "other city" },   
         { "ZipCode", "12345" },   
         { "Country", "test country" }   
        };  
       await _collection.InsertOneAsync(_document);  
     }  
   }  
 }  

If you need to rebuild indexes for a collection you can use the db.collection.reIndex() method to rebuild all indexes on a collection in a single operation. This operation drops all indexes, including the _id index, and then rebuilds all indexes.

Example:-

 db.users.reIndex()