C# WinForms CheckedChanged Not Fireing?

I have done a lot of reading on this and every question I found involves ASP.NET. I'm using Winforms. I have a checkbox (Called CheckboxPicture) on my main form. I want to run a few commands when the state of this checkbox is changed by the user.

This should do it:

    public void CheckboxPicture_CheckedChanged(Object sender, EventArgs e)
    {
        MessageBox.Show("Check State Changed");
    }

However checking and unchecking the checkbox dont work. ASP.NET says you need "Autopushback = true" but I'm not useing ASP.NET so im not sure where that would go.