将父类型的 ObservableCollection 转换为子类型

Question

I have class CheckBoxObject and DeployCheckBoxObject that derived from CheckBoxObject.

i have observable collection of CheckBoxObject and for each element of the collection want to use child properties and functions.

how can i convert the parent collection to child?

public class CheckboxObject : ViewModelBase
{
        public CheckboxObject(object o)
        {
            Object = o;
        }
        public object Object;
        public string Name => Object.ToString();
}

public class DeployCheckBoxObject : CheckboxObject
{
        public DeployCheckBoxObject(object o) : base(o)
        {

        }
        
        public string status { get; set; }
}

public class Test
{
        ObservableCollection<DeployCheckBoxObject> items = new ObservableCollection<DeployCheckBoxObject>();

public void populate(someObject) {

  items = someObject.ToObservableCheckboxCollection(); //error

  }

}

I also try to call child functions with parent object and get invalid cast error

public class Test
{
        ObservableCollection<CheckBoxObject> items = new ObservableCollection<CheckBoxObject>();

  public void populate(someObject) {

   items = someObject.ToObservableCheckboxCollection(); 
   foreach (CheckboxObject cb in CbVendorItems) {
     ((DeployCheckBoxObject)cb).Count = 100; //error
   }
  }

}

public static ObservableCollection<CheckboxObject> ToObservableCheckboxCollection<T>(this IEnumerable<T> enumerableList)
        {
            var a = new ObservableCollection<CheckboxObject>();
            if (enumerableList == null) return a;
            foreach (var item in enumerableList)
            {
                a.Add(new CheckboxObject(item));
            }
            return a;
        }

how can i access to child methods?

Answer 1

Do you know that all the CheckBoxObject s in your collection are actually DeployCheckBoxObject s, if so, then why not make your observable collection of the type DeployCheckBoxObject instead of CheckBoxObject

If you don't know for sure, and some CheckBoxObject s may not be a DeployCheckBoxObject then you need to check for type safety before casting

foreach (CheckboxObject cb in CbVendorItems)
{
    if (cb is DeployCheckBoxObject deployCb)
    {
        deployCb.Count = 100;
    }
}