How do you do a deep copy of an object in .NET?

Question

I want a true deep copy. In Java, this was easy, but how do you do it in C#?

Answer 1

Important Note

BinaryFormatter has been deprecated, and will no longer be available in .NET after November 2023. See BinaryFormatter Obsoletion Strategy

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I've seen a few different approaches to this, but I use a generic utility method as such:

public static T DeepClone<T>(this T obj)
{
 using (var ms = new MemoryStream())
 {
   var formatter = new BinaryFormatter();
   formatter.Serialize(ms, obj);
   ms.Position = 0;

   return (T) formatter.Deserialize(ms);
 }
}

Notes:

• Your class MUST be marked as [Serializable] for this to work.

• Your source file must include the following code:

   using System.Runtime.Serialization.Formatters.Binary;
   using System.IO;