mdi between form1 and form3 ifi click form2 button

Question

i have form1,form2 and form3.

form1 is my main mdi form.and also property set to ismdicontainer is true.

form1 buton click form 2 open

below code.

private void button1_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2();
f2.ShowDialog();
}

if i click form 2 button i want to open form3 in form1 with mdiparent and form2 will be close.

here is my code form 2 button click code

private void button1_Click(object sender, EventArgs e)
{
this.Hide();
Form3 f3 = new Form3();
f3.MdiParent = this.MdiParent;
f3.Show();
this.Close();
}

but form2 closed but form 3 is not set mdiparent.

pls help