What happens to C# Dictionary lookup if the key does not exist?

Question

I tried checking for null but the compiler warns that this condition will never occur. What should I be looking for?

Answer 1

Consider the option of encapsulating this particular dictionary and provide a method to return the value for that key:

public static class NumbersAdapter
{
    private static readonly Dictionary Mapping = new Dictionary
    {
        ["1"] = "One",
        ["2"] = "Two",
        ["3"] = "Three"
    };

    public static string GetValue(string key)
    {
        return Mapping.ContainsKey(key) ? Mapping[key] : key;
    }
}

Then you can manage the behaviour of this dictionary.

For example here: if the dictionary doesn't have the key, it returns key that you pass by parameter.