วน loop หาตำแหน่งของตัวเลขว่าอยู่ตำแหน่งที่เท่าไหร่บ้าง

public List<int> CheckNum(string txt)
{
    char[] chr = txt.ToCharArray(); // <--- เนี่ยๆๆๆๆ
    List<int> pos = new List<int>();

    for (int i = 0;i < chr.Count; i++)
    {
        if (Char.IsNumber(chr[i])) // <--- เนี่ยๆๆๆๆ
            pos.Add(i);
    }

    return pos;
}

    Public Class KeptNumberPatternArg
        Public RawString As String
        Public ResultList As ArrayList = New ArrayList()

        Public Sub New()
            'For i As Integer = 0 To 9
            '    Dim myList As List(Of Integer) = New List(Of Integer)()
            '    ResultList.Add(myList)
            'Next
        End Sub
    End Class

    ............
    ............
    ............

    Public Shared Function KeptNumberFromString(ByVal varInputString As String) As KeptNumberPatternArg
        Dim rData As KeptNumberPatternArg = New KeptNumberPatternArg()
        Dim tempStr As String = varInputString.Trim()

        rData.RawString = tempStr
        If (tempStr.Length > 0) Then

            For i As Integer = 0 To 9
                Dim NumCh As String = i.ToString()
                Dim iPos As Integer = 0
                Dim myList As List(Of Integer) = New List(Of Integer)()
                Do
                    iPos = tempStr.IndexOf(NumCh, iPos)
                    If (iPos >= 0) Then
                        myList.Add(iPos)
                    End If
                Loop Until (iPos = -1)
                rData.ResultList.Add(myList)
            Next

        End If

        Return rData
    End Function