CODEWITHSUNDEEP
c#mongodb
aaa
aaa

Reputation: 27

Mongodb c# retrieving element

I try to retrieve specific element from data base collection. 

collection.Find(new BsonDocument()).ForEachAsync(X => Console.WriteLine(X));

This code give something like this:

{ "_id" : ObjectId("599d420bf2e1abfed53fe3c6"), "no" : 9, "word" : "write" }

{ "_id" : ObjectId("599d420bf2e1abfed53fe3c8"), "no" : 10, "word" : "first" }

{ "_id" : ObjectId("599d420bf2e1abfed53fe3ca"), "no" : 11, "word" : "water" }

but I want to see only:

write
first
water

How can I do that? Thanks

Upvotes: 1

Views: 371

Answers (1)

dacke.geo
dacke.geo

Reputation: 343

Since I don't know what your data looks like, I've created my own as a test sample so you can see how I use projections to solve the problem. As you can see I've created a simple test collection call books that has a document with the property Word in it. It also has the implied "_id" property View from Studio 3T I created a small sample application in LINQPad to demonstrate.

// Define other methods and classes here
class Book
{
    public ObjectId _id { get; set; }
    public string Word { get; set; }
}

void Main()
{
    var mongoConnectionString = @"mongodb://Topaz:p%40$$w0rd@localhost";
    var client = new MongoDB.Driver.MongoClient(mongoConnectionString);
    var db = client.GetDatabase("Test");
    var col = db.GetCollection<Book>("Books");

    var filter = Builders<Book>.Filter.Empty;
    var projection = Builders<Book>.Projection.Expression(m => m.Word);
    var options = new FindOptions<Book, String> { BatchSize = 256, Projection = projection };

    var results = new List<string>();
    using (var cursor = col.FindAsync(filter, options).Result)
    {
        while (cursor.MoveNextAsync().Result)
        {
            var batch = cursor.Current as IList<String>;
            results.AddRange(batch);
        }
    }

    results.ForEach(a => Console.WriteLine(a)); 
}

Here is the output that I get. 

Foo
Bar

I hope this helps you. If it does, please mark my answer and let me know in a comment. Thank you.

Upvotes: 1

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