How to copy a String into another String in C#

In C#, there are several ways to copy a string into another string. Strings in C# are immutable, meaning they cannot be changed after creation. When you "copy" a string, you create a new string object with the same value.

Syntax

Following are the common syntaxes for copying strings in C# −

// Using String.Copy() method
string str2 = String.Copy(str1);

// Using direct assignment
string str2 = str1;

// Using string constructor
string str2 = new string(str1.ToCharArray());

Using String.Copy() Method

The String.Copy() method creates a new string object with the same value as the source string −

using System;
public class Demo {
   static public void Main(){
      string str1 = "Kevin";
      string str2 = String.Copy(str1);
      Console.WriteLine("String1 = " + str1);
      Console.WriteLine("String2 = " + str2);
      Console.WriteLine("Are they the same reference? " + ReferenceEquals(str1, str2));
   }
}

The output of the above code is −

String1 = Kevin
String2 = Kevin
Are they the same reference? False

Using Direct Assignment

Due to string interning in C#, direct assignment often results in the same reference for identical string literals −

using System;
public class Demo {
   static public void Main(){
      string str1 = "Maisie";
      string str2 = "Ryan";
      Console.WriteLine("String1 (Before copying) = " + str1);
      Console.WriteLine("String2 (Before copying) = " + str2);
      str2 = str1;  // Direct assignment
      Console.WriteLine("String1 = " + str1);
      Console.WriteLine("String2 (Updated) = " + str2);
      Console.WriteLine("Are they the same reference? " + ReferenceEquals(str1, str2));
   }
}

The output of the above code is −

String1 (Before copying) = Maisie
String2 (Before copying) = Ryan
String1 = Maisie
String2 (Updated) = Maisie
Are they the same reference? True

Using String Constructor

You can also create a new string by converting the original string to a character array −

using System;
public class Demo {
   static public void Main(){
      string str1 = "Hello World";
      string str2 = new string(str1.ToCharArray());
      Console.WriteLine("String1 = " + str1);
      Console.WriteLine("String2 = " + str2);
      Console.WriteLine("Are they equal? " + str1.Equals(str2));
      Console.WriteLine("Are they the same reference? " + ReferenceEquals(str1, str2));
   }
}

The output of the above code is −

String1 = Hello World
String2 = Hello World
Are they equal? True
Are they the same reference? False

Comparison of String Copying Methods

Conclusion

In most scenarios, direct assignment (str2 = str1) is sufficient for copying strings in C#. Use String.Copy() when you specifically need a new string instance, though this is rarely necessary due to string immutability.