Whereas one approach is to implement the ICloneable
interface (described here, so I won't regurgitate), here's a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code.
As mentioned elsewhere, it requires your objects to be serializable.
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
/// <summary>
/// Reference Article http://www.codeproject.com/KB/tips/SerializedObjectCloner.aspx
/// Provides a method for performing a deep copy of an object.
/// Binary Serialization is used to perform the copy.
/// </summary>
public static class ObjectCopier
{
/// <summary>
/// Perform a deep copy of the object via serialization.
/// </summary>
/// <typeparam name="T">The type of object being copied.</typeparam>
/// <param name="source">The object instance to copy.</param>
/// <returns>A deep copy of the object.</returns>
public static T Clone<T>(T source)
{
if (!typeof(T).IsSerializable)
{
throw new ArgumentException("The type must be serializable.", nameof(source));
}
// Don't serialize a null object, simply return the default for that object
if (ReferenceEquals(source, null)) return default;
using var Stream stream = new MemoryStream();
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(stream, source);
stream.Seek(0, SeekOrigin.Begin);
return (T)formatter.Deserialize(stream);
}
}
The idea is that it serializes your object and then deserializes it into a fresh object. The benefit is that you don't have to concern yourself about cloning everything when an object gets too complex.
In case of you prefer to use the new extension methods of C# 3.0, change the method to have the following signature:
public static T Clone<T>(this T source)
{
// ...
}
Now the method call simply becomes objectBeingCloned.Clone();
.
EDIT (January 10 2015) Thought I'd revisit this, to mention I recently started using (Newtonsoft) Json to do this, it should be lighter, and avoids the overhead of [Serializable] tags. (NB @atconway has pointed out in the comments that private members are not cloned using the JSON method)
/// <summary>
/// Perform a deep Copy of the object, using Json as a serialization method. NOTE: Private members are not cloned using this method.
/// </summary>
/// <typeparam name="T">The type of object being copied.</typeparam>
/// <param name="source">The object instance to copy.</param>
/// <returns>The copied object.</returns>
public static T CloneJson<T>(this T source)
{
// Don't serialize a null object, simply return the default for that object
if (ReferenceEquals(source, null)) return default;
// initialize inner objects individually
// for example in default constructor some list property initialized with some values,
// but in 'source' these items are cleaned -
// without ObjectCreationHandling.Replace default constructor values will be added to result
var deserializeSettings = new JsonSerializerSettings {ObjectCreationHandling = ObjectCreationHandling.Replace};
return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source), deserializeSettings);
}
C# language version history:
These are the versions of C# known about at the time of this writing:
- C# 1.0 released with .NET 1.0 and VS2002 (January 2002)
- C# 1.2 (bizarrely enough); released with .NET 1.1 and VS2003 (April 2003). First version to call
Dispose
on IEnumerator
s which implemented IDisposable
. A few other small features.
- C# 2.0 released with .NET 2.0 and VS2005 (November 2005). Major new features: generics, anonymous methods, nullable types, and iterator blocks
- C# 3.0 released with .NET 3.5 and VS2008 (November 2007). Major new features: lambda expressions, extension methods, expression trees, anonymous types, implicit typing (
var
), and query expressions
- C# 4.0 released with .NET 4 and VS2010 (April 2010). Major new features: late binding (
dynamic
), delegate and interface generic variance, more COM support, named arguments, tuple data type and optional parameters
- C# 5.0 released with .NET 4.5 and VS2012 (August 2012). Major features: async programming, and caller info attributes. Breaking change: loop variable closure.
- C# 6.0 released with .NET 4.6 and VS2015 (July 2015). Implemented by Roslyn. Features: initializers for automatically implemented properties, using directives to import static members, exception filters, element initializers,
await
in catch
and finally
, extension Add
methods in collection initializers.
- C# 7.0 released with .NET 4.7 and VS2017 (March 2017). Major new features: tuples, ref locals and ref return, pattern matching (including pattern-based switch statements), inline
out
parameter declarations, local functions, binary literals, digit separators, and arbitrary async returns.
- C# 7.1 released with VS2017 v15.3 (August 2017). New features: async main, tuple member name inference, default expression, and pattern matching with generics.
- C# 7.2 released with VS2017 v15.5 (November 2017). New features: private protected access modifier, Span<T>, aka interior pointer, aka stackonly struct, and everything else.
- C# 7.3 released with VS2017 v15.7 (May 2018). New features: enum, delegate and
unmanaged
generic type constraints. ref
reassignment. Unsafe improvements: stackalloc
initialization, unpinned indexed fixed
buffers, custom fixed
statements. Improved overloading resolution. Expression variables in initializers and queries. ==
and !=
defined for tuples. Auto-properties' backing fields can now be targeted by attributes.
- C# 8.0 released with .NET Core 3.0 and VS2019 v16.3 (September 2019). Major new features: nullable reference-types, asynchronous streams, indices and ranges, readonly members, using declarations, default interface methods, static local functions, and enhancement of interpolated verbatim strings.
- C# 9.0 released with .NET 5.0 and VS2019 v16.8 (November 2020). Major new features: init-only properties, records, with-expressions, data classes, positional records, top-level programs, improved pattern matching (simple type patterns, relational patterns, logical patterns), improved target typing (target-type
new
expressions, target typed ??
and ?
), and covariant returns. Minor features: relax ordering of ref
and partial
modifiers, parameter null checking, lambda discard parameters, native int
s, attributes on local functions, function pointers, static lambdas, extension GetEnumerator
, module initializers, and extending partial.
In response to the OP's question:
What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?
There is no such thing as C# 3.5 - the cause of confusion here is that the C# 3.0 is present in .NET 3.5. The language and framework are versioned independently, however - as is the CLR, which is at version 2.0 for .NET 2.0 through 3.5, .NET 4 introducing CLR 4.0, service packs notwithstanding. The CLR in .NET 4.5 has various improvements, but the versioning is unclear: in some places it may be referred to as CLR 4.5 (this MSDN page used to refer to it that way, for example), but the Environment.Version
property still reports 4.0.xxx.
As of May 3, 2017, the C# Language Team created a history of C# versions and features on their GitHub repository: Features Added in C# Language Versions. There is also a page that tracks upcoming and recently implemented language features.
Best Answer
Just to clear things up a bit:
RSA can be used either for encryption (ensuring that Eve cannot read messages that Alice sends to Bob) or for signing (ensuring that if Alice sends a message to Bob, Bob knows that it was actually Alice that sent the message, and not Eve pretending to be Alice)
RSA generates a pair of keys - a public key and a private key. RSA is designed so that if you apply the public key and then apply the private key, or vice versa, you will get the same message back. And the public key can be derived from the private key, but the opposite is impossible.
To use RSA for encryption, Alice encrypts the message using Bob's public key. The only way to read this message is with Bob's private key, which only he has. Thus Eve can't read the message because he does not have this key. On the other hand, this provides no authentication of the source of the message. Eve can also get Bob's public key (since it's public) and send messages to Bob, pretending to be Alice.
To use RSA for signing, Alice takes a hash of the message, encrypts the hash using her own private key, and appends the result (this is the signature) to the message. Eve can of course still decrypt this using Alice's public key. However, Bob can decrypt the signature using Alice's public key and see if it matches. If it does, it must have been encrypted using Alice's private key, which only she has, so it must have come from Alice.
Now, I'm not familiar with the .NET cryptography API, so I'm not sure if it works exactly as described here. But this explanation might help you understand some of the answers you are getting.