How to Retrieve a Dictionary Key from its Value in C#?

Retrieving Dictionary Key from a Given Value in C

In C#, obtaining the key of a dictionary item by its value requires a non-built-in solution since dictionaries inherently map unique keys to their associated values. Here's how you can achieve this:

Option 1: Using FirstOrDefault()

As values in a dictionary may not always be unique, we can perform a lookup operation to locate the desired key. The FirstOrDefault() method can be employed to search for the key-value pair that satisfies a given condition:

var myKey = types.FirstOrDefault(x => x.Value == "one").Key;

Option 2: Creating an Inverse Dictionary (when values are unique)

If we assume that values in the dictionary are unique and are inserted less frequently than being read, we can consider creating an inverse dictionary. This inverse dictionary would essentially swap the keys and values of the original dictionary, allowing us to retrieve the key by using the value. However, it's worth noting that this approach involves additional memory usage and storage overhead.

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