try this
Dim rb As New RadioButton()
For Each tr As TableRow In QuestionTable.Controls
For Each tc As TableCell In tr.Controls
If TypeOf tc.Controls(0) Is RadioButton Then
rb = DirectCast(tc.Controls(0), RadioButton)
If rb.Checked Then
Dim aa As String = rb.ID
End If
Exit For
End If
Next
Next
Hope this helps