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c#dictionarycase-insensitive
Ildar
Ildar

Reputation: 115

How to get original case key by case insensitive key in Dictionary<string, int>

There is Dictionary:

var dictionary1 = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase)
    {{"abc1", 1}, {"abC2", 2}, {"abc3", 3}};

I can get a value:

var value = dictionary1["Abc2"];

If search key "Abc2" I need to get the original key "abC2" and value 2.

How to get original case key by case insensitive key?

Upvotes: 4

Views: 403

Answers (2)

Sunil
Sunil

Reputation: 21396

You can use following code that utilizes LINQ to get dictionary key value pair even when case is not matching for key.

NOTE: This code can be used for dictionary of any size, but it's most appropriate for smaller size dictionaries since the LINQ is basically checking each key value pair one by one as opposed to directly going to the desired key value pair. 

Dictionary<string,int> dictionary1 = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase)
{
    {"abc1",1},
    {"abC2",2},
    {"abc3",3}
    } ;

var value1 = dictionary1["ABC2"];//this gives 2, even though case of key does not macth

//use LINQ to achieve your requirement
var keyValuePair1 = dictionary1.SingleOrDefault (d => d.Key.Equals("Abc2", StringComparison.OrdinalIgnoreCase) );

var key1 = keyValuePair1.Key ;//gives us abC2
var value2 =keyValuePair1.Value;//gives us 2

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1499810

You can't do that, unfortunately. It would be entirely reasonable for Dictionary<TKey, TValue> to expose a bool TryGetEntry(TKey key, KeyValuePair<TKey, TValue> entry) method, but it doesn't do so.

As stop-cran suggested in comments, the simplest approach is probably to make each value in your dictionary a pair with the same key as the key in the dictionary. So:

var dictionary = new Dictionary<string, KeyValuePair<string, int>>(StringComparer.OrdinalIgnoreCase)
{
    // You'd normally write a helper method to avoid having to specify
    // the key twice, of course.
    {"abc1", new KeyValuePair<string, int>("abc1", 1)},
    {"abC2", new KeyValuePair<string, int>("abC2", 2)},
    {"abc3", new KeyValuePair<string, int>("abc3", 3)}
};
if (dictionary.TryGetValue("Abc2", out var entry))
{
    Console.WriteLine(entry.Key); // abC2
    Console.WriteLine(entry.Value); // 2
}
else
{
    Console.WriteLine("Key not found"); // We don't get here in this example
}

If this is a field in a class, you could write helper methods to make it simpler. You could even write your own wrapper class around Dictionary to implement IDictionary<TKey, TValue> but add an extra TryGetEntry method, so that the caller never needs to know what the "inner" dictionary looks like.

Upvotes: 6

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