Pass textbox value from one form to another form

//Window1.xaml(Parent) 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    
        
        Cari
    

 //Window2.xaml(simple keyboard)
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window2" Height="148" Width="300">
    
        Q
        
        W
        E
        R
        T
        Y
        U
        I
        O
        P
        A
        S
        Enter
    

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

namespace WpfApplication1
{
    /// 

    /// Interaction logic for Window2.xaml
    /// 

    public partial class Window2 : Window
    {
        public Window2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "Q";
        }

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "W";
        }

        private void button3_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "E";
        }

        private void button4_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "R";
        }

        private void button5_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "T";
        }

        private void button6_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "Y";
        }

        private void button7_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "U";
        }

        private void button8_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "I";
        }

        private void button9_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "O";
        }

        private void button10_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "P";
        }

        private void button11_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "A";
        }

        private void button12_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "S";
        }

        private void button13_Click(object sender, RoutedEventArgs e)
        {
            Window1 form1 = new Window1();
            form1.textBox1.Text = textBox1.Text;
            form1.Show();//This is the problem
            Close();
        }
    }
}