c#属性一点疑问

public class A
{
//定义一个b属性
public B b
{
get
{
return new B();  //每次get均调用
}
}
//public B b = new B();   只调用一次
}

return new B();

public RelayCommand EditCommand {
get {
return new RelayCommand(() => {
CurrentEmployee.BeginEdit();
});
}
}