How to compare two Dictionaries in C#
algorithm, c#, collections, data-structures, dictionary
Solution
If you've already checked that the keys are the same, you can just use:
var dict3 = dict2.Where(entry => dict1[entry.Key] != entry.Value)
.ToDictionary(entry => entry.Key, entry => entry.Value);
To explain, this will:
- Iterate over the key/value pairs in `dict2`
- For each entry, look up the value in `dict1` and filter out any entries where the two values are the same
- Form a dictionary from the remaining entries (i.e. the ones where the `dict1` value is different) by taking the key and value from each pair just as they appear in `dict2`.
Note that this avoids relying on the equality of `KeyValuePair<TKey, TValue>` - it might be okay to rely on that, but personally I find this clearer. (It will also work when you're using a custom equality comparer for the dictionary keys - although you'd need to pass that to `ToDictionary`, too.)
Problem
I have two generic Dictionaries. Both have the same keys, but their values can be different. I want to compare the 2nd dictionary with the 1st dictionary. If there are differences between their values, I want to store those values in a separate dictionary. ``` 1st Dictionary ------------ key Value Barcode 1234566666 Price 20.00 2nd Dictionary -------------- key Value Barcode 1234566666 Price 40.00 3rd Dictionary -------------- key Value Price 40 ``` Can anyone give me the best algorithm to do this? I wrote an algorithm but it has a lot of loops. I am seeking a short and efficient idea, like a solution using LINQ query expressions or LINQ lambda expressions. I am using .NET Framework 3.5 with C#. I found something about the `Except()` method, but unfortunately I couldn't understand what is happening on that method. It would be great if anyone could explain the suggested algorithm.