Extract numbers from an AlphaNumeric string
If you want to extract both at the same time (I don't know if it is a requirement, it isn't clear in the question) you should iterate once through each character to place them in different lists.

  Dim input As String = "sdff45hg589&gt;@#DF456&amp;&lt;jk778P&amp;&amp;FHJ75"
  Dim characters As List(Of Char) = New List(Of Char)()
  Dim numbers As List(Of Char) = New List(Of Char)()
  For Each c As Char In input
     If (Char.IsNumber(c)) Then
        numbers.Add(c)
     ElseIf (Char.IsLetter(c)) Then
        characters.Add(c)
     End If
  Next

'Do whatever you have to do here


Edit

As pointed out @mjolka, since the goal of the user is to show the splitted numbers and letters, a StringBuilder would be more appropriate. Here is my updated answer : 

  Dim input As String = "sdff45hg589&gt;@#DF456&amp;&lt;jk778P&amp;&amp;FHJ75"
  Dim characters As StringBuilder = New StringBuilder()
  Dim numbers As StringBuilder = New StringBuilder()
  For Each c As Char In input
     If (Char.IsNumber(c)) Then
        numbers.Append(c)
     ElseIf (Char.IsLetter(c)) Then
        characters.Append(c)
     End If
  Next

'Do whatever you have to do here