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

Submitted by: @import:stackoverflow-api·Mar 10, 2026·

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netobjectyouhowdeepcopy

Problem

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

Solution

Important Note

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

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

public static T DeepClone(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;

Code Snippets

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);
 }
}

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

Context

Stack Overflow Q#129389, score: 735

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