Why are Checkboxes not seen as being of type Checkbox?

This question morphed from a previous one here.

It seems that the problem is actually this failure to recognize checkboxes as such - whether there's really a problem with updating the database once this conundrum is solved remains to be seen.

So here's the code:

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim connStr As String = "SERVER=PLATYPUS42;DATABASE=duckbilldata;UID=entenhausen;PWD=pondscum"
    Dim upd8DML As String = "UPDATE CustomerCategoryLog SET Category = 'Exploding' WHERE Unit = @Unit And MemberNo = @MemberNo AND Custno = @CustNo"

    Dim coName As String
    Dim argVals(2) As String
    Dim _Unit As String
    Dim _MemberNo As String
    Dim _CustNo As String
    Dim curCheckboxIDVal As String
    Label2.Text="label 2 text from button1_click"
    LabelDebug.Text="label debug text from button1_click"

    For Each cntrl As Control In Me.Controls
            Label2.Text="label 2 text from foreach"
            If TypeOf cntrl Is CheckBox Then
                Label2.Text="label 2 text from is checkbox"
                If DirectCast(cntrl, CheckBox).Checked = True Then
                    Label2.Text="label 2 text from checked"
                    curCheckboxIDVal = CStr(DirectCast(cntrl, CheckBox).ID)
                    coName = GetLabelTextForID(curCheckboxIDVal)
                    argVals = GetArgValsForCompanyName(coName)
                    _Unit = argVals(0)
                    _MemberNo = argVals(1)
                    _CustNo = argVals(2)
                Label2.Text=_Unit
                LabelDebug.Text=_MemberNo
                    Using conn As New SqlConnection(connStr), _
                        cmd As New SqlCommand(upd8DML, conn)
                        cmd.Parameters.Add("@Unit", SqlDbType.VarChar, 50).Value = _Unit
                        cmd.Parameters.Add("@MemberNo", SqlDbType.VarChar, 50).Value = _MemberNo
                        cmd.Parameters.Add("@CustNo", SqlDbType.VarChar, 50).Value = _CustNo
                        conn.Open
                        cmd.ExecuteScalar()
                    End Using
                End If
            End If
        Next
End Sub

I am updating Label2.Text to see how far the code gets - and it only gets to the "foreach" - this is the last value of Label2.Text: "label 2 text from foreach"

So this line:

If TypeOf cntrl Is CheckBox Then

...fails to equate to true.

Yet, not only do I have many dynamically-created Checkboxes on the form when the button is clicked, there is also one that I dropped there at design-time. NONE of these checkboxes are seen as checkboxes, obviously.

Why not? Why is the type of the checkbox control not evaluating to CheckBox?

NOTE: When I prepend "the whole shebang" like so:

System.Web.UI.WebControls.CheckBox

...it makes no difference; in fact, it grays out the "System.Web.UI.WebControls." portion.