DataGridViewColumnHeaderCell attempts to open with a designer

I have a class derived from a DataGridViewColumnHeaderCell. When I attempt to open the file for viewing, VS attempts to open the file with a designer.

I'm not sure what designates the file as having a designer. The DataGridViewColumnHeaderCell doesn't have one.

Is there a way to prevent VS from trying to open the file with a designer?

My Imports are:

Code:

---

Imports System
Imports System.ComponentModel
Imports System.Windows.Forms.VisualStyles
Imports System.Reflection

---

I've attached my source file.

There is a ListBox as a Private Internal class to my class.

This is what VS is seeing and is causing the error.

I can do one of the following:
1. Put a simple class derived from Control before my class in its file
2. Move the internal ListBox class to a different file.
3. Make a designer or attach one to my class.