Linq: Except on two different types of dictionaries

Question

i have 2 different types of dictionaries Dictionary<int, Fooclass> oldDic and Dictionary<int, string> barList newDic . Now i need to compare values in both dictionaries. for Example key can be in

• oldDic : 1,2,3
• newDic : 1,2,3,4
• Expected Output : 4

Now i need to compare both dictionaries on basis of their keys any help would be appreciated.

Edit : Output should be like second dictionary(newDic) but this will contain some value of 2nd dictionary's(oldDic). For example

1,"fooString" Where fooString is some value in Fooclass's someproperty.... For more clarity see this which doesn't worked for me

var addedList = from list1 in baseListDic
join list2 in trackerlist on list1.Key equals list2.Key
 select new { key = list1.Key, value = list1.Value._lead };

here baseListDic is oldDic and trackerlist is newDic.... Let me know if i'm still not clear...

Answer 1

It would be easier to just create a new dictionary based on the new dictionary ignoring items that have the same key in the old dictionary.

var result = newDic
    .Where(kvp => !oldDic.ContainsKey(kvp.Key))
    .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

Answer 2

Note: Despite your question saying "i need to compare values in both dictionaries" (emphasis mine) your example seems to be demonstrating just comparison of keys so I've gone with that. If it is values you need to compare you might want to give an example of what you mean and if they are easily convertible or comparable...

If you are only actually comparing the keys then you can just use the .Keys property of the dictionary which returns an IEnumerable<TKey> that you can do your linq on...

eg:

var expectedOutput = newDic.Keys.Except(oldDic.Keys);

This does rely on the key being the same type but this goes without saying if you are comparing. Of course, there is nothing stopping you from converting their types first if you do wnat to do this with different types.

Also if you wanted to then get the values in one of the dictionaries you could do something like:

var newDicValues = expectedoutput.Select(x=>newDic[x]);

Or, you know, do any other linqy stuff you feel like. :)