using System;
using System.Globalization;
class CountryLookup
{
// ------------------------------------------------------------
// GetCountryName
// Receives a 2‑letter ISO country code (alpha‑2) and returns
// the corresponding country name.
//
// RegionInfo understands ISO‑3166 codes and exposes the
// localized country name via DisplayName.
//
// If the code is invalid, the method returns null to signal
// that no country could be resolved.
// ------------------------------------------------------------
static string GetCountryName(string alpha2)
{
try
{
// Normalize input: trim whitespace and convert to uppercase
string normalized = alpha2.Trim().ToUpperInvariant();
// RegionInfo can be constructed directly from an ISO alpha‑2 code
var region = new RegionInfo(normalized);
// DisplayName provides the human‑friendly country name
return region.DisplayName;
}
catch (ArgumentException)
{
// Thrown when the code is invalid; return null to indicate failure
return null;
}
}
// ------------------------------------------------------------
// Main
// Demonstrates the lookup function with several sample codes.
// ------------------------------------------------------------
static void Main()
{
string[] codes = { "US", "GB", "FR", "ZZ" }; // ZZ is intentionally invalid
foreach (var code in codes)
{
string name = GetCountryName(code);
if (name != null) {
Console.WriteLine($"{code} → {name}");
}
else {
Console.WriteLine($"{code} → (invalid code)");
}
}
}
}
/*
run:
US → United States
GB → United Kingdom
FR → France
ZZ → (invalid code)
*/
