Just realized how wrong that code was, which I wrote early in the project.
This should work, from the docs. I just tried it and it's kind of there but still showing the border/resize grip, but probably because I changed lots of properties of my form when experimenting.
Configuring the Parent Form
C#VB.NET
private void Form1_Load(object sender, EventArgs e)
{
this.IsMdiContainer = true;
this.radDock1.AutoDetectMdiChildren = true;
}
3. Add a form to the project that will serve the role of child form. No properties, methods or event handlers need to be set for this form, except that you may want to add some content that will be visible when the child forms are displayed as tabbed documents.
4. Add code to the parent form to create the child form and assign it an MDI parent:
C#VB.NET
private void radMenuItem1_Click(object sender, EventArgs e)
{
Form childForm = new Form();
childForm.Text = "MDI Child " + DateTime.Now.ToShortTimeString();
childForm.MdiParent = this;
childForm.Show();
}