How to Clone/Deep Copy a .Net Generic Dictionary<String, T>

What is the best way to clone/deep copy a .NET generic Dictionary string, T ?

Okay, the .NET 2.0 answers:

If you don't need to clone the values, you can use the constructor overload to Dictionary which takes an existing IDictionary. (You can specify the comparer as the existing dictionary's comparer, too.)

If you do need to clone the values, you can use something like this:

public static Dictionary<TKey, TValue> CloneDictionaryCloningValues<TKey, TValue>
   (Dictionary<TKey, TValue> original) where TValue : ICloneable
{
    Dictionary<TKey, TValue> ret = new Dictionary<TKey, TValue>(original.Count,
                                                            original.Comparer);
    foreach (KeyValuePair<TKey, TValue> entry in original)
    {
        ret.Add(entry.Key, (TValue) entry.Value.Clone());
    }
    return ret;
}

That relies on TValue.Clone() being a suitably deep clone as well, of course.

How do you clone a dictionary in .NET?

Use the Constructor that takes a Dictionary. See this example

var dict = new Dictionary<string, string>();

dict.Add("SO", "StackOverflow");

var secondDict = new Dictionary<string, string>(dict);

dict = null;

Console.WriteLine(secondDict["SO"]);

And just for fun.. You can use LINQ! Which is a bit more Generic approach.

var secondDict = (from x in dict
                  select x).ToDictionary(x => x.Key, x => x.Value);

Edit

This should work well with Reference Types, I tried the following:

internal class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public User Parent { get; set; }
}

And the modified code from above

var dict = new Dictionary<string, User>();

dict.Add("First", new User 
    { Id = 1, Name = "Filip Ekberg", Parent = null });

dict.Add("Second", new User 
    { Id = 2, Name = "Test test", Parent = dict["First"] });

var secondDict = (from x in dict
                  select x).ToDictionary(x => x.Key, x => x.Value);

dict.Clear();

dict = null;

Console.WriteLine(secondDict["First"].Name);

Which outputs "Filip Ekberg".

What is the best way to clone/deep copy a .NET generic Dictionary string, T ?

Okay, the .NET 2.0 answers:

If you don't need to clone the values, you can use the constructor overload to Dictionary which takes an existing IDictionary. (You can specify the comparer as the existing dictionary's comparer, too.)

If you do need to clone the values, you can use something like this:

public static Dictionary<TKey, TValue> CloneDictionaryCloningValues<TKey, TValue>
   (Dictionary<TKey, TValue> original) where TValue : ICloneable
{
    Dictionary<TKey, TValue> ret = new Dictionary<TKey, TValue>(original.Count,
                                                            original.Comparer);
    foreach (KeyValuePair<TKey, TValue> entry in original)
    {
        ret.Add(entry.Key, (TValue) entry.Value.Clone());
    }
    return ret;
}

That relies on TValue.Clone() being a suitably deep clone as well, of course.

Make a deep copy of a dictionary

You don't need to change the CloneDictionaryCloningValues method at all, if you make the myData class implement the ICloneable interface:

public class myData : ICloneable {

  // your code

  public object Clone() {
    // whatever you need to create a copy, for example:
    return new myData() {
      age = this.age,
      nationality = this.nationality,
      income = this.income
    };
  }

}

You can also rewrite/overload the method to take a cloning method instead of demanding the IClonable interface:

public static Dictionary<TKey, TValue> CloneDictionaryCloningValues<TKey, TValue>
   (Dictionary<TKey, TValue> original, Func<TValue, TValue> clone)
{
  Dictionary<TKey, TValue> ret = new Dictionary<TKey, TValue>(original.Count, original.Comparer);
  foreach (KeyValuePair<TKey, TValue> entry in original) {
    ret.Add(entry.Key, clone(Value));
  }
  return ret;
}

Then you call the method with a function that creates a copy of an item:

myCopy = CloneDictionaryCloningValues(myOriginal, item => {
  // whatever you need to create a copy, for example:
  return new myData() {
    age = item.age,
    nationality = item.nationality,
    income = item.income
  };
});

How do I copy the content of a dictionary to an new dictionary in C#?

Assuming you mean you want them to be individual objects, and not references to the same object pass the source dictionary into the destination's constructor:

Dictionary<string, string> d = new Dictionary<string, string>();
Dictionary<string, string> d2 = new Dictionary<string, string>(d);

"so that they are not the same object."

Ambiguity abound - if you do actually want them to be references to the same object:

Dictionary<string, string> d = new Dictionary<string, string>();
Dictionary<string, string> d2 = d;

(Changing either d or d2 after the above will affect both)

How to deep copy a Dictionary containing a List in C#?

You need to deep-copy the lists as well; all you have done is copy the dictionary, but all of the list references are still shared between them.

This is fairly easy using LINQ:

var tmpStudents = students.ToDictionary(p => p.Key, p => p.Value.ToList());

How to make a deep copy Dictionary template

You can use Generics with where TValue : ICloneable constraint:

public static Dictionary<TKey, TValue> deepCopyDic<TKey, TValue>(Dictionary<TKey, TValue> src)
    where TValue : ICloneable
{
    //Copies a dictionary with all of its elements
    //RETURN:
    //      = Dictionary copy
    Dictionary<TKey, TValue> dic = new Dictionary<TKey, TValue>();
    foreach (var item in src)
    {
        dic.Add(item.Key, (TValue)item.Value.Clone());
    }

    return dic;
}

You'll have to implement ICloneable interface in every class you'd like to pass into that method.

Or a bit improved version, with Key cloned as well:

public static Dictionary<TKey, TValue> deepCopyDic<TKey, TValue>(Dictionary<TKey, TValue> src)
    where TValue : ICloneable
    where TKey : ICloneable
{
    return src.ToDictionary(i => (TKey)i.Key.Clone(), i => (TValue)i.Value.Clone());
}

How to copy a dictionary containing reference type for value to another dictionary in C#

You're looking to do a "deep copy." See Jon Skeet's answer here.

How to make deep copy of a dictionary within Dictionary in c#?

I do not know what you are trying to do in the workflow, but why not to reinstancing instead of cleaning?

dict_set.Clear(); 

to:

dict_set = new Dictionary<string, string>(); 

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