Time for action – one-to-many mapping

Here is the first problem:

Suppose, we have a List of names and we want to index them as per the first two letters of these names:

  1. Copy the following code snippet as a query to LINQPad:
    string[] firstNames = { "Samuel", "Jenny", "Joyace", "Sam" };
    var map = firstNames.ToLookup(c => c.Length);
    foreach (var m in map)
      foreach (var n in m)
        Console.WriteLine("--" + n);
  2. Run the query and you should get the following output:
    Time for action – one-to-many mapping

What just happened?

ToLookup() creates what you can imagine as a one-to-many Dictionary.

The Lambda expression c => c.Length describes the key to be used for the ...

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