Comparing two dictionaries (Key, value) and return Keys that doesn't have same value

Question

I'm bit new to c# and want to identify keys that doesn't have same value while comparing two dictionaries.

The dictionary I have is of dict => KeyValuePair<string, string>. And I have two dictionaries like -

dict1 => {"a":"False","b":"amazonaws.com","c":"True"}
dict2 => {"a":"True","b":"amazonaws.com","c":"False"}

I want to compare both dictionaries and return a variable which will have Keys ["a", "c"] as for the above example, those keys have different value.

Currently the logic I have written will only differentiate keys that's not there in the other dictionary.

Dictionary dictExcept = null;
foreach (IDictionary kvp in dict1.Cast<object>().Where(kvp => !dict2.Contains(kvp)))
    {
        dictExcept.Add(kvp.Keys, kvp.Values);
    }
return dictExcept ;

Answer 1

You can try using TryGetValue:

using System.Linq;

...

var dictExcept = dict1
  .Where(pair => dict2.TryGetValue(pair.Key, out var value) && 
                 pair.Value != value)
  .ToDictionary(pair => pair.Key, 
                pair => (first: pair.Value, second: dict2[pair.Key]));

Here we for each key value pair from dict1 try to get corresponding value from dict2:

// dict2 has pair.Key it corresponds to value...
dict2.TryGetValue(pair.Key, out var value) && 
// however value from dict2 != value from dict1
pair.Value != value

The very same idea if you prefer to use foreach (no Linq solution):

var dictExcept = new Dictionary<string, (string first, string second)>();

foreach (var pair in dict1)
  if (dict2.TryGetValue(pair.Key, out var value) && value != pair.Value)
    dictExcept.Add(pair.Key, (pair.Value, value)); 

Demo: (fiddle)

  var dict1 = new Dictionary<string, string> { 
    { "a", "False" }, { "b", "False" }, { "c", "True" }, { "d", "dict1 only" } };

  var dict2 = new Dictionary<string, string> { 
    { "a", "False" }, { "b", "True" }, { "c", "False" }, { "e", "dict2 only" } };

  var dictExcept = dict1
    .Where(pair => dict2.TryGetValue(pair.Key, out var value) &&
                   pair.Value != value)
    .ToDictionary(pair => pair.Key,
                  pair => (first: pair.Value, second: dict2[pair.Key]));

  string report = string.Join(Environment.NewLine, dictExcept
    .Select(pair => $"Key: {pair.Key}; Values: {pair.Value}"));

  Console.Write(report);

Outcome:

Key: b; Values: (False, True)
Key: c; Values: (True, False)