C# winForm subform accesses the controls of the parent form

Form part:

Form1: Main form (IsMdiContainer property is set to true, Modifiers property of textBox1 is set to public)

Form2: Subform

 

Code part:

//parent form

　　Form2 f2 = new Form2();
　　f2.Owner = this;
　   f2.ShowDialog();

// Child body

     Form1 f1=new Form1();
     f1=(Form1)this.Owner;
     f1.textBox1.Text="Subform accesses main form";