How do you do a deep copy an object in .Net (C# specifically)?

Question

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

Answer 1

I'm still on the C# learning curve, but when I looked into this it appeared that you had to roll your own deep copy function if you wanted one.

Answer 2

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

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

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

Note that your class MUST be marked as [Serializable] in order for this to work.

Answer 3

this is one way: http://www.thomashapp.com/node/106 another is to use binary serialization.

Answer 4

What does a Deep Copy do? Does it copy the bitstream?

Answer 5

Have you tried using the struct construct? I'm a newbie to c# myself (also coming from the Java camp) but this may be useful to you.

http://www.c-sharpcorner.com/UploadFile/rajeshvs/StructuresInCS11112005234341PM/StructuresInCS.aspx

I.e.

With structs you can do this (psuedo code):

A = 10;
B = A;
B = 20

print(A) // out's 10
print(B) // out's 20

Kind of like java primatives, but structs can have methods and other variables just as regular classes

Answer 6

Kilhoffer's code doesn't compile. Here's the corrected version.

    public static T DeepCopy<T>(T obj)
    {
        object result = null;

        using (var ms = new MemoryStream())
        {
            var formatter = new BinaryFormatter();
            formatter.Serialize(ms, obj);
            ms.Position = 0;

            result = (T)formatter.Deserialize(ms);
            ms.Close();
        }

        return (T)result;
    }

Answer 7

Building on Kilhoffer's solution...

With C# 3.0 you can create an extension method as follows:

public static class ExtensionMethods
{
    // Deep clone
    public static T DeepClone<T>(this T a)
    {
        using (MemoryStream stream = new MemoryStream())
        {
            BinaryFormatter formatter = new BinaryFormatter();
            formatter.Serialize(stream, a);
            stream.Position = 0;
            return (T) formatter.Deserialize(stream);
        }
    }
}

which extends any class that's been marked as [Serializable] with a DeepClone method

MyClass copy = obj.DeepClone();