CODEWITHSUNDEEP
c#
Rod
Rod

Reputation: 15477

compare dictionaries

i have 3 generic dictionaries

static void Main(string[] args)
{
    Dictionary<string, string> input = new Dictionary<string, string>();
    input.Add("KEY1", "Key1");

    Dictionary<string, string> compare = new Dictionary<string, string>();
    compare.Add("KEY1", "Key1");
    compare.Add("KEY2", "Key2");
    compare.Add("KEY3", "Key3");

    Dictionary<string, string> results = new Dictionary<string, string>();

i'd like to take the list of input and compare each value to the compareTo list and if it doesn't exist add it to the results list?

Upvotes: 1

Views: 333

Answers (2)

James Michael Hare
James Michael Hare

Reputation: 38417

You can use the LINQ Except() method:

        foreach (var pair in compare.Except(input))
        {
            results[pair.Key] = pair.Value;
        }

This will perform a set difference (in effect subtracting input from compare and returning what is left over), which we can then add to the results dictionary.

Now, if results has no previous values, and you just want it to be the results from that current operation, you can just do that directly:

      var results = compare.Except(input)
                           .ToDictionary(pair => pair.Key, pair => pair.Value);

This is assuming you want the difference in keys and values. If you had a different value (same key), it would show in the difference.

That is, for your example above results will have:

[KEY2, Key2]
[KEY3, Key3]

But if your example data was:

        Dictionary<string, string> input = new Dictionary<string, string>();
        input.Add("KEY1", "Key1");

        Dictionary<string, string> compare = new Dictionary<string, string>();
        compare.Add("KEY1", "X");
        compare.Add("KEY2", "Key2");
        compare.Add("KEY3", "Key3");

The results would be:

[KEY1, X]
[KEY2, Key2]
[KEY3, Key3]

Due to the fact KEY1's value was different.

If you do want only where keys or values are not contained in the other, you can do the Except on the Keys or Values collections of the dictionary instead.

Upvotes: 2

escargot agile
escargot agile

Reputation: 22389

dict[key] gives you the value whose key is key.

dict.ContainsKey(key) and dict.ContainsValue(value) are methods you can use to check whether a key or a value are in the dictionary. ContainsKey is more time-efficient.

Upvotes: 1

Related Questions