How to recursively Iterate over properties of an Entity

问题

Suppose this is what I have in my database


table Ancestor (  
  idAncestor int not null,  
  name varchar(20) not null,  
)  

table Descendant (  
  idDescendant int not null,  
  name varchar(20) not null,  
  Ancestor_idAncestor int not null  
)

When ADO.NET generates the entity object for the above 2 tables, I can access Descendant of Ancestor through Ancestors.First().Descendants.

If I were to recursively iterate over an ancestor's descendant(s) or descendant's descendant(s) and print out its id and name, the following is my attempt


public void Iterate(Ancestor a)  
{  
   Type t = a.GetType();
   PropertyInfo[] props = t.GetProperties();
   foreach(var prop in props){
      // pseudo code here
      if(prop is entitycollection)
      {
         // how do I convert prop to entity collection here??
         foreach(var p in prop){
            Iterate(p)
         }         
      } else {
         print prop.GetValue(a, null)
      }
   }       
}

My problem is trying to figure out if a entity property is of entity collection, if it is, then find the type hold by the collection, then iterate over the type, and so on.

Thanks

回答1:

This should be a crude version of what you're looking for:

private static void recurseAndPrintProperties(Object ObjectToRecurse) {
   foreach (PropertyInfo pi in ObjectToRecurse.GetType().GetProperties()) {
       if ((pi.PropertyType.IsGenericType && pi.PropertyType.GetGenericTypeDefinition() == typeof(EntityCollection<>))) {
           IEnumerable collection = (IEnumerable)pi.GetValue(ObjectToRecurse, null);

           foreach (object val in collection)
               recurseAndPrintProperties(val);
       } else {
            if (pi.PropertyType == typeof(Descendant)) {
                Descendant actualDescendant = (Descendant)pi.GetValue(ObjectToRecurse, null);
                Console.WriteLine(actualDescendant.idDescendant + " - " + actualDescendant.Name);
            } else
                Console.WriteLine(pi.Name + "  -  " + pi.GetValue(ObjectToRecurse, null));
       }
   }
}

EDIT

This code came from some code I had previously played around with for cloning entities. Here it is (you might have to modify it to also take into consideration not duplicating your properties thar are mapped to primary keys)

    public static T CloneEntity<T>(T Obj) where T : EntityObject, new() {
        T Clone = new T();

        Type typeToClone = Obj.GetType();
        Type[] BadGenericTypes = new Type[] { typeof(EntityCollection<>), typeof(EntityReference<>) };
        Type[] BadTypes = new Type[] { typeof(System.Data.EntityKey) };

        foreach (PropertyInfo pi in typeToClone.GetProperties().Where(p => p.CanWrite)) {
            if (pi.PropertyType.IsGenericType && BadGenericTypes.Contains(pi.PropertyType.GetGenericTypeDefinition())
                || (BadTypes.Contains(pi.PropertyType))
                || (pi.Name.Equals(Extension.GetPropertyName(() => new FMVHistory().FMVHistoryId), StringComparison.CurrentCultureIgnoreCase)))
                continue;

            pi.SetValue(Clone, pi.GetValue(Obj, null), null);
        }
        return Clone;
    }

来源：https://stackoverflow.com/questions/5381851/how-to-recursively-iterate-over-properties-of-an-entity

标签

reflection

ado.net

enumeration