What is the best way to iterate over a dictionary?

Question

I\'ve seen a few different ways to iterate over a dictionary in C#. Is there a standard way?

Answer 1

With .NET Framework 4.7 one can use decomposition

var fruits = new Dictionary<string, int>();
...
foreach (var (fruit, number) in fruits)
{
    Console.WriteLine(fruit + ": " + number);
}

To make this code work on lower C# versions, add System.ValueTuple NuGet package and write somewhere

public static class MyExtensions
{
    public static void Deconstruct<T1, T2>(this KeyValuePair<T1, T2> tuple,
        out T1 key, out T2 value)
    {
        key = tuple.Key;
        value = tuple.Value;
    }
}

Answer 2

foreach(KeyValuePair<string, string> entry in myDictionary)
{
    // do something with entry.Value or entry.Key
}

Answer 3

If you are trying to use a generic Dictionary in C# like you would use an associative array in another language:

foreach(var item in myDictionary)
{
  foo(item.Key);
  bar(item.Value);
}

Or, if you only need to iterate over the collection of keys, use

foreach(var item in myDictionary.Keys)
{
  foo(item);
}

And lastly, if you're only interested in the values:

foreach(var item in myDictionary.Values)
{
  foo(item);
}

(Take note that the var keyword is an optional C# 3.0 and above feature, you could also use the exact type of your keys/values here)

Answer 4

I would say foreach is the standard way, though it obviously depends on what you're looking for

foreach(var kvp in my_dictionary) {
  ...
}

Is that what you're looking for?

Answer 5

I wrote an extension to loop over a dictionary.

public static class DictionaryExtension
{
    public static void ForEach<T1, T2>(this Dictionary<T1, T2> dictionary, Action<T1, T2> action) {
        foreach(KeyValuePair<T1, T2> keyValue in dictionary) {
            action(keyValue.Key, keyValue.Value);
        }
    }
}

Then you can call

myDictionary.ForEach((x,y) => Console.WriteLine(x + " - " + y));

Answer 6

I will take the advantage of .NET 4.0+ and provide an updated answer to the originally accepted one:

foreach(var entry in MyDic)
{
    // do something with entry.Value or entry.Key
}