c# - How to cast a Generic<T> to a Generic<R> where T is a subclass of R? -

is there way define explicit converter or similar such compiler can automatically populate generic<t> generic<r> where t : r ?

the error message is:

the value "reference1[dog]" not of type "reference1[pet]" , cannot used in generic collection.

my reference class looks this:

public interface ireference<t> {     t value { get; } }  public class reference<t> : ireference<t> {     #region properties     public string ref_type { get; set; }     public string ref_id { get; set; }     public uri href { get; set; }      private bool resolved = false;     private t _value = default(t);      public t value     {                  {             if( !resolved && href != null ) resolve();             else if( href == null ) return null;             return _value;         }     }     #endregion      #region constructors     public reference() { }     public reference(string ref_id)      {         this.ref_id = ref_id;     }     #endregion      #region members     private void resolve()     {         if( href != null )         {             _value = apirequestmethods.geturi<t>(href);             resolved = true;         }         else             throw new exception("cannot resolve reference because href property has not been set.");     }     #endregion } 

this work if generic type interface, , make generic type covariant, ie: igeneric<out t>.

note work interfaces or delegates. details, see covariance , contravariance in generics.