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

I've got a generic dictionary Dictionary<string, T> that I would like to essentially make a Clone() of ..any suggestions.

Solution 1:

(Note: although the cloning version is potentially useful, for a simple shallow copy the constructor I mention in the other post is a better option.)

How deep do you want the copy to be, and what version of .NET are you using? I suspect that a LINQ call to ToDictionary, specifying both the key and element selector, will be the easiest way to go if you're using .NET 3.5.

For instance, if you don't mind the value being a shallow clone:

var newDictionary = oldDictionary.ToDictionary(entry => entry.Key,
                                               entry => entry.Value);

If you've already constrained T to implement ICloneable:

var newDictionary = oldDictionary.ToDictionary(entry => entry.Key, 
                                               entry => (T) entry.Value.Clone());

(Those are untested, but should work.)

Solution 2:

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.

Solution 3:

Dictionary<string, int> dictionary = new Dictionary<string, int>();

Dictionary<string, int> copy = new Dictionary<string, int>(dictionary);

Solution 4:

That's what helped me, when I was trying to deep copy a Dictionary < string, string >

Dictionary<string, string> dict2 = new Dictionary<string, string>(dict);

Good luck