C# MongoDB driver - need simple code to read/query collection

Question

I am new to MongoDB and I am using the C# driver, version: v4.0.30319: using MongoDB.Bson; using MongoDB.Driver;

First sorry for this probably being a simple question and I am just not able to find what I need correctly with correct search terms to make this work.

For my project. I am able to connect to the DB, get a list of all the collections, and loop through one of the collections using ASYNC. The problem I am having is trying to find examples to work for simple things like count, limit, or to find/get specific records.

Most of the examples appear to be an older version then what I am using and all what I can find requires ASYNC.

Here is a function I have that is working and returning data.

I want to be able to have a function that works that will and return sub sets of data (using a query), get a count, and other simple things.

My data in the collection is:

_id
RocketRequestID  int
LoanRocketID     int
RequestDate      date
CreatedByID      int
RequestXML       string/xml doc

My function is:

 static async Task<int>MainAsync()
    {

        int CountRecords = 0;

        var client = new MongoDatabaseConnection().mongoConn();

        IMongoDatabase db = client.GetDatabase("Viper");

        var collection = db.GetCollection<BsonDocument>("RocketRequest");            

        using (IAsyncCursor<BsonDocument> cursor = await collection.FindAsync(new BsonDocument()))
        {                
            while (await cursor.MoveNextAsync())
            {
                IEnumerable<BsonDocument> batch = cursor.Current;
                foreach (BsonDocument document in batch)
                {
                    Console.WriteLine(document);
                    Console.WriteLine();
                }
            }
        }// end using

        return CountRecords;

    }// end async

Again this is probably something simple and I apologize but appreciate any help you can give.

Alex · Accepted Answer · 2017-01-09 14:44:08Z

3

You could create an object to map to your collection:

public class RocketRequest
{
    public string Id { get; set; }
    public int RocketRequestID { get; set; }
    public int LoanRocketID { get; set; }

    public DateTime RequestDate { get; set; }

    public int CreatedByID { get; set; }

    public string RequestXML { get; set; }
}

Then try using Linq by adding the following using statement

using MongoDB.Driver.Linq;

You can then write simpler queries like (for example)

var collection = db.GetCollection<RocketRequest>("RocketRequest");   
var count = collection.AsQueryable<Employee>()
              .Count();

answered Jan 9, 2017 at 14:44

Alex

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2 Comments

Brad Over a year ago

Alex, looks good, I think the Linq part is the thing I was missing. One question you have: var count = collection.AsQueryable<Employee>() .Count(); I assume that supposed to be <RocketRequest> and not <Employee>. I made that change and I am able to get the count, thank you.

Brad Over a year ago

I just need to add the find, and loops through the code, but with adding the Linq stuff to it I thing I can get that worked out. and populate the class with the data

Fabiano Arruda · Accepted Answer · 2017-01-09 15:01:08Z

you can try using something like this:

    public async Task<Round> GetRound(int id)
    {
        IMongoCollection<Round> collection = m_db.GetCollection<Round>("Rounds");
        FilterDefinition<Round> filter = Builders<Round>.Filter.Eq("Round", id);

        return await collection.Find(filter).SingleOrDefaultAsync();
    }

I execute a filter by Id, also, you can use the method Count() instead SingleOrDefaultAsync(), of course, you will need to change your return type for that.

    public async Task<long> GetRoundCount(int id)
    {
        IMongoCollection<Round> collection = m_db.GetCollection<Round>("Rounds");
        FilterDefinition<Round> filter = Builders<Round>.Filter.Eq("Round", id);

        return await Task.Run(() => collection.Find(filter).Count());
    }

Thom · Accepted Answer · 2019-05-22 09:54:55Z

0

Use IFindFlient to retrieve your data:

For example:

var items = collection.Find(x => x.CreatedByID == 1).ToEnumerable()

Or

var itemsCount = collection.Find(x => x.RequestDate >= dateToSearch).Count()

You could use class and loading of collection, which is suggested in the answer of @Alex. It's a good explanation of how to create a collection object and mapping class:

public class RocketRequest
{
    public string Id { get; set; }
    public int RocketRequestID { get; set; }
    public int LoanRocketID { get; set; }    
    public DateTime RequestDate { get; set; }    
    public int CreatedByID { get; set; }    
    public string RequestXML { get; set; }
}

var collection = db.GetCollection<RocketRequest>("RocketRequest");

edited May 22, 2019 at 9:54

Thom

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answered Jan 9, 2017 at 14:48

Maksim Simkin

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