Comparing 2 Dictionary Instances

Question

I want to compare the contents of two Dictionary instances regardless of the order of the items they contain. SequenceEquals

Answer 1

This will check if all Values from source exists in target, ignoring the Keys

var result = source.All(x => target.Any(y => x.Value == y.Value));

Answer 2

var contentsEqual = source.DictionaryEqual(target);

// ...

public static bool DictionaryEqual<TKey, TValue>(
    this IDictionary<TKey, TValue> first, IDictionary<TKey, TValue> second)
{
    return first.DictionaryEqual(second, null);
}

public static bool DictionaryEqual<TKey, TValue>(
    this IDictionary<TKey, TValue> first, IDictionary<TKey, TValue> second,
    IEqualityComparer<TValue> valueComparer)
{
    if (first == second) return true;
    if ((first == null) || (second == null)) return false;
    if (first.Count != second.Count) return false;

    valueComparer = valueComparer ?? EqualityComparer<TValue>.Default;

    foreach (var kvp in first)
    {
        TValue secondValue;
        if (!second.TryGetValue(kvp.Key, out secondValue)) return false;
        if (!valueComparer.Equals(kvp.Value, secondValue)) return false;
    }
    return true;
}

Answer 3

If you use a SortedDictionary you won't need to apply the sorting yourself, which can be slightly easier to use:

void Main()
{
    var d1 = new Dictionary<string, string>
    {
        ["a"] = "Hi there!",
        ["b"] = "asd",
        ["c"] = "def"
    };
    var d2 = new Dictionary<string, string>
    {
        ["b"] = "asd",
        ["a"] = "Hi there!",
        ["c"] = "def"
    };

    var sortedDictionary1 = new SortedDictionary<string, string>(d1);
    var sortedDictionary2 = new SortedDictionary<string, string>(d2);

    if (sortedDictionary1.SequenceEqual(sortedDictionary2))
    {
        Console.WriteLine("Match!");
    }
    else
    {
        Console.WriteLine("Not match!");
    }
}

Answer 4

I don't know if there is an existing method but you could use the following (null checking of args omitted for brevity)

public static bool DictionaryEquals<TKey,TValue>(
  this Dictionary<TKey,TValue> left,
  Dictionary<TKey,TValue> right ) { 

  var comp = EqualityComparer<TValue>.Default;
  if ( left.Count != right.Count ) { 
    return false;
  }
  foreach ( var pair in left ) {
    TValue value;
    if ( !right.TryGetValue(pair.Key, out value) 
         || !comp.Equals(pair.Value, value) ) {
      return false;
    }
  } 
  return true;
}

It would be best to add an overload to allow customization of the EqualityComparer<TValue>.