Question

I have a C# class called “SmallClass”.

I have an existing list myList containing objects of type “SmallClass”

I want a deep clone of the list “myList”. That is, deep Clone the containing list and deep clone the objects contained in the list.

How should I do this.

    public class SmallClass: ICloneable {

    public string str1;
    public string str2;
    public string str3;

     public SmallClass Clone() //This just deep clones 1 object of type "SmallClass"
            {
                MemoryStream m = new MemoryStream();
                BinaryFormatter b = new BinaryFormatter();
                b.Serialize(m, this);
                m.Position = 0;
                return (SRO)b.Deserialize(m);
            }

      public override equals(Object a)
        {
                return Object.Equals(this.str1 && a.str1);
            }
    }

    public class AnotherClass
    {
           SomeCode();
           List<SmallClass> myList = new List<SmallList>();  //myList is initialized.


           // NOW I want to deep clone myList. deep Clone the containing list and deep clone the objects contained in the list.

         List<SmallClass> newList = new List<SmallClass>();
      foreach(var item in myList)
        {
           newList.Add((SmallClass)item.Clone());
        }       

}

Answer 1

Warning: The BinaryFormatter type is dangerous when used with untrusted input. Whilst the usage below should be safe, Microsoft recommend avoiding BinaryFormatter altogether due to its potential for misuse, and will remove it from .NET 7–8. Consider using another serializer or approach for your deep clones.

First off, you can define a utility method for deep-cloning any object (root):

public static T DeepClone<T>(T obj)
{
    using (var stream = new MemoryStream())
    {
        var formatter = new BinaryFormatter();
        formatter.Serialize(stream, obj);
        stream.Position = 0;
        return (T)formatter.Deserialize(stream);
    }
}

If you want to deep-clone myList, all you need to do is pass it as parameter to the method above:

List<SmallClass> myListClone = DeepClone(myList);

The most important consideration you need to pay attention to is that all your classes must be marked as serializable, typically through the [SerializableAttribute].

[SerializableAttribute]
public class SmallClass
{
    // …
}