Option Strict On, set Focus to unknown object type

I am updating some code to allow Option Strict On. One of the problems that comes up is late binding. I have one Form

with several required elements of different types ( TextBox

, ComboBox

etc.). I have a validation function Form

and then setting focus to the first control that doesn't matter.

Without the Strict On option, I could just create a base one Object

and set it depending on which control is missing and then call it objMissing.Focus()

at the end, but with the Strict On option, the compiler does not allow late binding.

I understand that if the controls were of the same type, I could, for example, pass the missing object to TextBox

. Is there a way I can still do this using a single variable to keep the control to set focus? Or should I just set Focus at once in each of the ones If

that check the value?

Here is the example code I'm looking for (txt_ are TextBox

, cbo_ are ComboBox

, btn_ are Button

types):

    Dim objMissing as Object

    If txtItemDescription.Text = String.Empty Then
        objMissing = txtItemDescription
        strMessage = "You must enter an item description."
    ElseIf cboProductType.Text = String.Empty Then
        objMissing = cboProductType
        strMessage = "You must select a product type."
    ElseIf cboComponentType.Text = String.Empty And cboComponentType.Enabled Then
        objMissing = cboComponentType
        strMessage = "You must select a component type."
    ElseIf txtOnHand.Text = String.Empty Then
        txtOnHand.Text = "0"
    ElseIf txtRented.Text = String.Empty Then
        txtRented.Text = "0"
    ElseIf txtCost.Text = String.Empty Then
        txtCost.Text = "0.00"
    ElseIf txtFreight.Text = String.Empty Then
        txtFreight.Text = "0.00"
    ElseIf Len(txtBarcodePrefix.Text) < 6 Then
        objMissing = txtBarcodePrefix
        strMessage = "You must enter a 6-digit barcode prefix."
    ElseIf cboCondition.Text = String.Empty Then
        objMissing = cboCondition
        strMessage = "You must enter a condition."
    ElseIf btnComponents.Enabled And Me.ComponentList.Count = 0 Then
        objMissing = btnComponents
        strMessage = "You must select the item components."
    ElseIf txtSerialNumber.Text <> String.Empty AndAlso txtOnHand.Text <> String.Empty Then
        If CInt(txtOnHand.Text) > 1 Then
            objMissing = txtOnHand
            strMessage = "You cannot have more than 1 item on hand with the same serial number."
        End If
    End If

    If objMissing IsNot Nothing Then
        MessageBox.Show(strMessage)
        objMissing.Focus()
    End If