Function SumDigits Learn programming Visual Basic (VB.net)

Imports System
Public Class exercise113
    Public Shared Function SumDigits(ByVal n As Integer) As Integer
        Dim number As String = Convert.ToString(n)
        Dim sum As Integer = 0

        For i As Integer = 0 To number.Length - 1
            sum += Convert.ToInt32(number.Substring(i, 1))
        Next

        Return sum
    End Function

    Public Shared Sub Main()
        Console.WriteLine(SumDigits(123))
    End Sub
End Class