Adding a dictionary to another [duplicate]

Question

Possible Duplicates:
Merging dictionaries in C#
What's the fastest way to copy the values and keys from one dictionary into another in C#?

I have a dictionary that has some values in it, say:

Animals <string, string> 

I now receive another similar dictionary, say:

NewAnimals <string,string> 

How can I append the entire NewAnimals dictionary to Animals?

Answer 1

foreach(var newAnimal in NewAnimals)     Animals.Add(newAnimal.Key,newAnimal.Value) 

Note: this throws an exception on a duplicate key.

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Or if you really want to go the extension method route(I wouldn't), then you could define a general AddRange extension method that works on any ICollection<T>, and not just on Dictionary<TKey,TValue>.

public static void AddRange<T>(this ICollection<T> target, IEnumerable<T> source) {     if(target==null)       throw new ArgumentNullException(nameof(target));     if(source==null)       throw new ArgumentNullException(nameof(source));     foreach(var element in source)         target.Add(element); } 

(throws on duplicate keys for dictionaries)

Answer 2

Create an Extension Method most likely you will want to use this more than once and this prevents duplicate code.

Implementation:

 public static void AddRange<T, S>(this Dictionary<T, S> source, Dictionary<T, S> collection)  {         if (collection == null)         {             throw new ArgumentNullException("Collection is null");         }          foreach (var item in collection)         {             if(!source.ContainsKey(item.Key)){                 source.Add(item.Key, item.Value);             }             else             {                // handle duplicate key issue here             }           }   } 

Usage:

Dictionary<string,string> animals = new Dictionary<string,string>(); Dictionary<string,string> newanimals = new Dictionary<string,string>();  animals.AddRange(newanimals);