how to use function "findone" in c#

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I am studying mongodb.
the below code is ok.

XML

using (var mongo = new Mongo(connectionstring))
            {
                mongo.Connect();
                var db = mongo.GetDatabase(dbName);
                var connection = db.GetCollection<Customer>();
                  
                Customer customer = connection.FindOne(x => x.CustomerID == "001");
                
                return customer;
            }

But when using Expression,I can not get the result.Why?

XML

using (var mongo = new Mongo(connectionstring))
            {
                mongo.Connect();
                var db = mongo.GetDatabase(dbName);
                var connection = db.GetCollection<Customer>();
                Func<Customer, bool> exp = x => x.CustomerID == "001";               
                Customer customer = connection.FindOne(exp);
                return customer;
            }

Posted 9-Dec-13 16:11pm

cyousyun

Updated 9-Dec-13 16:15pm

v4

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cyousyun 10-Dec-13 0:58am

Thanks for your solution.but what i want to do is to pass parameter to findone.as below.
public class MongoDBBase<t> where T:class
{
private static string connectionstring = "Server=127.0.0.1:28013";
private static string dbName = "blog";

public T GetOne(Func<t,bool> func)
{
using (var mongo = new Mongo(connectionstring))
{
mongo.Connect();
var db = mongo.GetDatabase(dbName);
var connection = db.GetCollection<t>();
var t= connection.FindOne(func);
return t;
}
}
}

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sankarsan parida · Answer 1 · 2013-12-09T18:23:00

See First Know what to do
In MongoDatabase Format you are using FindOne method from a Mongo Collection
N.B.

connection.FindOne(IMongoQuery query);
It Means query usually a QueryDocument or constructed using the QueryBuilder
For this suggestion Use IMongoQuery

  IMongoQuery query = Query.EQ("CustomerID", "001");
  Customer customer = connection.FindOne(query);