MongoSampleUsage.cs

MongoConfiguration.Initialize(c => c.AddMap<PersonMap>());
using (var db = Mongo.Create("mongodb://localhost/test"))
{
     var people = db.GetCollection<Person>();
     people.Save(new Person { FirstName = "myfirst", LastName = "mylast" });
     var person = (from p in people.AsQueryable()
                   where p.FirstName == "myfirst"
                   select p).Single();
     Console.WriteLine(person.FirstName + " " + person.LastName);
}

PersonMongo.cs

public class Person
{
    public Person()
    {
        Id = Guid.NewGuid();
    }       
    public Guid Id { get; set; }        
    public string FirstName { get; set; }        
    public string LastName { get; set; }        
    public bool Equals(Person other)
    {
        if (ReferenceEquals(null, other)) return false; 
        if (ReferenceEquals(this, other)) return true;
        return other.Id.Equals(Id);
    }        
    
    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != typeof (Person)) return false;
        return Equals((Person) obj);
    }  
    
    public override int GetHashCode()
    {
        return Id.GetHashCode();
    }
}

PersonMongoMap.cs

public class PersonMap : MongoConfigurationMap
{
    public PersonMap()
    {
        For<Person>(config => config.IdIs(p => p.Id));
    }
}