c# - Structuremap ObjectFactory.GetAllInstances inserts null value into list -

i have simple list instantiating structuremaps objectfactory.getallinstances().

private list<userreleasetime> _userreleasetimes =      objectfactory.getallinstances<userreleasetime>().tolist() 

userreleasetime looks this:

public class userreleasetime {     public string name { get; set; }     public double totalreleasetime { get; set; }     public double withinreleasehours { get; set; }     public double outsidereleasehours { get; set; } } 

after collection created appears structuremap adds 1 object empty or null values. there anyway stop happening?

update: userreleasetime registered structuremap this:

for<userreleasetime>().use<userreleasetime>();