C# Shallow copy Dictionary?

Question

I need to shallow copy a dictionary in c#.

For instance:

Dictionary<int,int> flags = new Dictionary<int,int>();
flags[1] = 2;
flags[2] = 3;
flags[0] = 9001;
Dictionary<int,int> flagsn = flags.MemberwiseClone();

Unfortunately, that returns the error: "error CS1540: Cannot access protected member object.MemberwiseClone()' via a qualifier of typeSystem.Collections.Generic.Dictionary'. The qualifier must be of type `PointFlagger' or derived from it"

Not entirely sure what this means... Is there another way to shallow copy a dictionary/fix my code above?

score 62 · Accepted Answer · answered Jan 14 '12 at 00:46

62

To get a shallow copy, just use the constructor of Dictionary<TKey, TValue> as it takes an IEnumerable<KeyValuePair<TKey, TValue>>. It will add this collection into the new instance.

Dictionary<int, int> flagsn = new Dictionary<int, int>(flags);

answered Jan 14 '12 at 00:46

JaredPar

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@Jared, Actually, it seems it doesn't accept an `IEnumerable`, but a `IDictionary dictionary` – Mar 10 '16 at 08:31

score 10 · Answer 2 · answered Mar 14 '12 at 15:29

10

This is a generic way I found where you don't have to explicitly write any type, which I prefer for maintainability reasons:

var ShallowCopy = OriginalDictionary.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

answered Mar 14 '12 at 15:29

gatopeich

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What is "kvp => kvp.Key, kvp => kvp.Value" in this context. How will i add key and value. It showing an error at my end – Pratik Jul 30 '13 at 04:56
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You need to add a using statement for `System.Linq` to access the ToDictionary() extension method. – Johnathon Sullinger Aug 12 '14 at 02:23
I would strongly advise against doing this. The LINQ call is useful for deep copying, but has huge negative performance implications if all you want is a shallow copy. – Dmitri Nesteruk Feb 22 '21 at 10:09

C# Shallow copy Dictionary?

2 Answers2