Imports System
Imports System.Globalization
Module CountryLookup
'------------------------------------------------------------
' GetCountryName
' A small, focused function that receives a 2-letter ISO code
' and returns the corresponding country name.
'
' Uses RegionInfo, which is part of the .NET Framework and
' understands ISO-3166 country codes. If the code is invalid,
' the function returns Nothing to signal failure.
'------------------------------------------------------------
Function GetCountryName(alpha2 As String) As String
Try
' Normalize input: trim whitespace and convert to uppercase
Dim normalized As String = alpha2.Trim().ToUpperInvariant()
' RegionInfo can be constructed from an ISO alpha-2 code
Dim region As New RegionInfo(normalized)
' RegionInfo.DisplayName gives the localized country name
Return region.DisplayName
Catch ex As ArgumentException
' Thrown when the code is invalid; return Nothing to indicate no match
Return Nothing
End Try
End Function
'------------------------------------------------------------
' Main
' Demonstrates the function with a few sample codes.
'------------------------------------------------------------
Sub Main()
Dim codes() As String = {"US", "GB", "FR", "ZZ"} ' ZZ is intentionally invalid
For Each code In codes
Dim name As String = GetCountryName(code)
If name IsNot Nothing Then
Console.WriteLine($"{code} → {name}")
Else
Console.WriteLine($"{code} → (invalid code)")
End If
Next
End Sub
End Module
' run:
'
' US → United States
' GB → United Kingdom
' FR → France
' ZZ → (invalid code)
'
