which imports statement is useful when you use the streamwriter class?

If Single.TryParse(txtHours.Text, sngNumHours) Then
' If you don't input anything within the hours worked text box
MessageBox.Show("Must enter a number of hours worked")
With txtHours
.Focus()
.SelectAll()
End With
Return
End If
If Single.TryParse(txtPay.Text, sngPayrate) Then
'If you don't input a pay rate
MessageBox.Show("You must input a pay rate")
With txtHours
.Focus()
.SelectAll()
End With
Return
End If