Look at the code below.

Code:
((Form1(this.Owner).textBox1.Text  = "new value";
((Form1(this.Owner).textBox2.Text  = "new value";
((Form1(this.Owner).textBox3.Text  = "new value";
vs

Code:
Form1 f1 = (Form1)this.Owner;
f1.textBox1.Text  = "new value";
f1.textBox2.Text  = "new value";
f1.textBox3.Text  = "new value";

thanks