private void MainForm_Load(object sender, EventArgs e)

{

NavigationForm w = new NavigationForm();

ShowForm(w);

}

public void ShowForm(Form form1)

{

this.panel3.Controls.Clear();

form1.TopLevel = false;

form1.FormBorderStyle = FormBorderStyle.None;

form1.Dock = DockStyle.Fill;

form1.Parent = this.panel3;

this.panel3.Controls.Add(form1);

form1.Show();

}