public partial class Form1 : Form //父窗体
 {
   public string name="";
   public Form1()
   {
     InitializeComponent();
   }
   private void newBtn_Click(object sender, EventArgs e)
   {
     Form2 form2 =new Form2();
     form2.ShowDialog();
     if (form2.DialogResult == DialogResult.OK)
     {
       textBox1.Text = form2.name;
       form2.Close();
     }
   }
 }

public partial class Form2 : Form // 子窗体
  {
    public string name
   {
      set { textBox1.Text = value; }
      get { return textBox1.Text; }
    }
    public Form2()
    {
      InitializeComponent();
    }
    private void OK_Click(object sender, EventArgs e)
    {
      if (textBox1.Text == "")
      {
        MessageBox.Show("input!");
        return;
      }
      DialogResult = DialogResult.OK;
      Close();
    }
  }

public partial class Form1 : Form //parent form
 
  {
    public string name="";
    public Form1()
    {
      InitializeComponent();
    }
    private void newBtn_Click(object sender, EventArgs e)
    {
      Form2 form2 =new Form2();
      form2.Owner = this;//form2的指针指向form1
      form2.ShowDialog();
      textBox1.Text = form2.name;
      form2.Close(); 
    }
  }

public partial class Form2 : Form //son form
  {
    public string name
   {
      set { textBox1.Text = value; }
      get { return textBox1.Text; }
    }
    public Form2()
    {
      InitializeComponent();
    }
    private void OK_Click(object sender, EventArgs e)
    {
      if (textBox1.Text == "")
      {
        MessageBox.Show("input!");
        return;
      }
      Form1 form1 = (Form1)this.Owner;//form2的父窗体指针赋给form1
      Close();
    }
  }