Child form controls not showing up

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C#

C#4.0

MDI

I'm playing around with MDI (I know, I know...torturing myself. I guess I like pain.) and have an issue with child form controls not showing up after setting the child form dockstyle to fill when the child form is created.

Parent Form:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace mdiparent_example
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void closeToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Dispose();

        }

        private void childWindow1ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form ChildForm1 = new Form();
            ChildForm1.MdiParent = this;
            // ChildForm1.FormBorderStyle = FormBorderStyle.None;
            ChildForm1.Dock = DockStyle.Fill;
            ChildForm1.Show();

        }

        private void childWindow2ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form ChildForm2 = new Form();
            ChildForm2.MdiParent = this;
            // ChildForm2.FormBorderStyle = FormBorderStyle.None;
            ChildForm2.Dock = DockStyle.Fill;
            ChildForm2.Show();

        }
    }
}

Child form:

namespace mdiparent_example
{
    public partial class ChildForm1 : Form
    {
        public ChildForm1()
        {
            InitializeComponent();


        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Dispose();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Dispose();

        }
    }
}

Both of the Child forms are the same except for their names.

Any ideas on what is causing this? What solutions might be around?

Thanks,
Sig Pimp