Adding Custom Properties At Run Time

[khan]

Hi!

does any one know how to add custom properties to a class or component at
runtime.?
actually we want our user to add custom properties at desing time including default properties. eg.
i have a class
let say UserNode
class UserNode
{
private string username;
private string lastname;

public string UserName
{
get
{
}
set{}
}
}
now if user want to add some other information about himself let say social security number. how could it be possible?

thanks