I am trying to update my form based on the selected index from my combo box but am getting errors. I suspect that I have to convert some data but am not able to get around it. Here is my error/code:

Error:
An unhandled exception of type 'System.InvalidCastException' occurred in system.data.dll

Additional information: Object must implement IConvertible.

Code:
Private Sub cbProdName_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbProdName.SelectedIndexChanged
'displays product info based on the item selected

If cbProdName.SelectedIndex <> -1 Then

'clear ProdInfo data set
dsProdInfoObj.Clear()

'look up data based on combo box selection
daProdInfo.SelectCommand.Parameters("ProductID").Value = cbProdName.SelectedValue

'fill the data set
daProdInfo.Fill(dsProdInfoObj)

'convert data
'txtProdID.Text = CInt(txtProdID.Text)
'txtUnitPrice.Text = CDec(txtUnitPrice.Text)
'txtUnitStock.Text = CInt(txtUnitStock.Text)

End If
End Sub

With these lines:
'convert data
txtProdID.Text = CInt(txtProdID.Text)
txtUnitPrice.Text = CDec(txtUnitPrice.Text)
txtUnitStock.Text = CInt(txtUnitStock.Text)

I get this error:

An unhandled exception of type 'System.InvalidCastException' occurred in system.data.dll

Additional information: Object must implement IConvertible.