Imports System.Runtime.CompilerServices

Module ExtensionExample

    Sub Main()

        Console.WriteLine("ExtensionExample.vb")
        Console.Write("Enter a number between 1 and 10 ==> ")

        Dim i As Integer = Integer.Parse(Console.ReadLine())

        Console.WriteLine("The value is {0} ", _
                          IIf(i.CheckRange(1, 10), i, "out of range"))

        Console.Write("Enter one of these values {CA | NY | TX | FL | NC} ==> ")
        Dim state As String = Console.ReadLine().ToUpper()

        Console.WriteLine("The state is {0} ", _
                          IIf(state.CheckValues("CA", "NY", "TX", "FL", "NC"), state, " not in the list"))

        Console.WriteLine("End of tester")
        Console.ReadLine()

    End Sub

End Module

Module CheckExtensions

    ''' <summary>
    ''' Extension method that adds a range checking feature to integer data.
    ''' </summary>
    ''' <param name="number">The integer value to check.</param>
    ''' <param name="lowValue">The inclusive low value of the range to check.</param>
    ''' <param name="highValue">The inclusive high value of the range to check.</param>
    ''' <returns>Boolean indicating whether or not the value is within the range.</returns>
    <Extension()> _
    Public Function CheckRange(ByVal number As Integer, _
                               ByVal lowValue As Integer, _
                               ByVal highValue As Integer) _
           As Boolean

        If ((number >= lowValue) AndAlso (number <= highValue)) Then
            Return True
        Else
            Return False
        End If

    End Function

    ''' <summary>
    ''' Extension method that adds a list of values checking feature to string data.
    ''' </summary>
    ''' <param name="testValue">The string value to check.</param>
    ''' <param name="values">A comma-delimited list of string values that are the
    ''' valid values.</param>
    ''' <returns>Boolean indicating whether or not the value is in the list.</returns>
    <Extension()> _
    Public Function CheckValues(ByVal testValue As String, _
                                ByVal ParamArray values() As String) _
           As Boolean

        If (values.Contains(testValue)) Then
            Return True
        Else
            Return False
        End If

    End Function

End Module