<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Content="Button 1" Height="23" HorizontalAlignment="Left" Margin="99,103,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
        <Button Content="Button 2" Height="23" HorizontalAlignment="Left" Margin="305,103,0,0" Name="button2" VerticalAlignment="Top" Width="75" Click="button2_Click" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="99,33,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="260,33,0,0" Name="textBox2" VerticalAlignment="Top" Width="120" />
    </Grid>
</Window>

private void button1_Click(object sender, RoutedEventArgs e)
        {
            MessageBox.Show(textBox1.Text);
            button1.IsEnabled = false;
        }

private void button2_Click(object sender, RoutedEventArgs e)
        {
            MessageBox.Show(textBox2.Text);
        }

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="309" Width="474" Loaded="Window_Loaded">
    <Grid Height="248" Width="442">
        <Button Content="Bấm Vào" Height="23" HorizontalAlignment="Left" Margin="171,189,0,0" Name="buttonBamVao" VerticalAlignment="Top" Width="75" Click="buttonBamVao_Click" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="93,60,0,0" Name="textBoxSo" VerticalAlignment="Top" Width="120" TextChanged="textBox1_TextChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="293,60,0,0" Name="textBoxChuoi" VerticalAlignment="Top" Width="120" TextChanged="textBoxChuoi_TextChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="205,144,0,0" Name="textBoxKetQua" VerticalAlignment="Top" Width="120" TextChanged="textBoxKetQua_TextChanged" />
        <Button Content="Nhấn Để Lưu" Height="23" HorizontalAlignment="Left" Margin="171,98,0,0" Name="buttonLuu" VerticalAlignment="Top" Width="75" Click="buttonLuu_Click" />
        <TextBlock Height="23" HorizontalAlignment="Left" Margin="25,60,0,0" Name="textBlock1" Text="Nhập Số" VerticalAlignment="Top" />
        <TextBlock Height="23" HorizontalAlignment="Left" Margin="224,60,0,0" Name="textBlock2" Text="Nhập Chuỗi" VerticalAlignment="Top" />
        <TextBlock Height="23" HorizontalAlignment="Left" Margin="93,144,0,0" Name="textBlock3" Text="Nhập Gì Cũng Được" VerticalAlignment="Top" />
    </Grid>
</Window>

using System;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        bool danhapso = false;
        bool danhapchuoi = false;

        string so = "";
        string chuoi = "";

        public MainWindow()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                if (Char.IsDigit(c) || Char.IsControl(c)) newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;
            if (textBox.Text.Length != 0)
            {
                danhapso = true;
                if (danhapchuoi == true)
                {
                    buttonLuu.IsEnabled = true;
                }
            }
            else
            {
                danhapso = false;
                buttonLuu.IsEnabled = false;
            }
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            textBoxSo.Focus();
            buttonLuu.IsEnabled = false;
            buttonBamVao.IsEnabled = false;
        }

        private void textBoxChuoi_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                danhapchuoi = true;
                if (danhapso == true)
                {
                    buttonLuu.IsEnabled = true;
                }
            }
            else
            {
                danhapchuoi = false;
                buttonLuu.IsEnabled = false;
            }
        }

        private void buttonLuu_Click(object sender, RoutedEventArgs e)
        {
            buttonLuu.IsEnabled = false;
            textBoxChuoi.IsEnabled = false;
            textBoxSo.IsEnabled = false;
            so = textBoxSo.Text;
            chuoi = textBoxChuoi.Text;
        }

        private void textBoxKetQua_TextChanged(object sender, TextChangedEventArgs e)
        {
          TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0 && buttonLuu.IsEnabled == false && danhapchuoi == true && danhapso == true)
            {
                buttonBamVao.IsEnabled = true;
            }
            else
            {
                buttonBamVao.IsEnabled = false;
            }
        }

        private void buttonBamVao_Click(object sender, RoutedEventArgs e)
        {
            string s = textBoxKetQua.Text;
            bool toanlaso = true;
            foreach (Char c in s)
            {
                if (!Char.IsDigit(c))
                {
                    toanlaso = false;
                    break;
                }
            }
            if (toanlaso == true)
            {
                textBoxKetQua.Text = textBoxChuoi.Text;
            }
        }
    }
}

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Grid>
        <ComboBox Height="23" HorizontalAlignment="Left" Margin="172,40,0,0" Name="comboBox1" VerticalAlignment="Top" Width="120" SelectionChanged="comboBox1_SelectionChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="172,105,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" />
        <Label Content="Chọn Số" Height="28" HorizontalAlignment="Left" Margin="111,40,0,0" Name="label1" VerticalAlignment="Top" />
        <Label Content="Kết Quả" Height="28" HorizontalAlignment="Left" Margin="113,100,0,0" Name="label2" VerticalAlignment="Top" />
        <CheckBox Content="Mở Ra!" Height="16" HorizontalAlignment="Left" Margin="330,45,0,0" Name="checkBoxMora" VerticalAlignment="Top" Checked="checkBoxMora_Checked" Unchecked="checkBoxMora_Unchecked" />
    </Grid>
</Window>

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.Navigation;
using System.Windows.Shapes;

namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        string[] Chu = { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"};
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            int i;
            for (i = 0; i < 10; i++)
            {
                comboBox1.Items.Add(i + 1);
            }
            comboBox1.SelectedIndex = 0;
            [You must be registered and logged in to see this link.] = Chu[0];
            comboBox1.IsEnabled = false;
        }

        private void comboBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            textBox1.Text = Chu[comboBox1.SelectedIndex];
        }

        private void checkBoxMora_Checked(object sender, RoutedEventArgs e)
        {
            comboBox1.IsEnabled = true;
        }

        private void checkBoxMora_Unchecked(object sender, RoutedEventArgs e)
        {
            comboBox1.IsEnabled = false;
        }
    }
}

<Window x:Class="WpfApplication4.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Grid>
        <Button Content="Xuất" Height="23" HorizontalAlignment="Left" Margin="187,214,0,0" Name="buttonXuat" VerticalAlignment="Top" Width="75" Click="buttonXuat_Click" />
        <Button Content="Lưu" Height="23" HorizontalAlignment="Left" Margin="187,117,0,0" Name="buttonLuu" VerticalAlignment="Top" Width="75" Click="buttonLuu_Click" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="63,65,0,0" Name="textBoxSo" VerticalAlignment="Top" Width="120" TextChanged="textBox1_TextChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="265,65,0,0" Name="textBoxChuoi" VerticalAlignment="Top" Width="120" TextChanged="textBoxChuoi_TextChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="63,165,0,0" Name="textBoxXuat" VerticalAlignment="Top" Width="120" TextChanged="textBoxXuat_TextChanged" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="265,165,0,0" Name="textBoxXuatChu" VerticalAlignment="Top" Width="120" />
    </Grid>
</Window>

using System;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        bool danhapso = false;
        bool danhapchuoi = false;

        string chuoi = "";

        public MainWindow()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                if (Char.IsDigit(c) || Char.IsControl(c)) newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                danhapso = true;
                if (danhapchuoi == true)
                {
                    buttonLuu.IsEnabled = true;
                }
            }
            else
            {
                danhapso = false;
                buttonLuu.IsEnabled = false;
            }
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            textBoxSo.Focus();
            buttonLuu.IsEnabled = false;
            buttonXuat.IsEnabled = false;
        }

        private void textBoxChuoi_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                danhapchuoi = true;
                if (danhapso == true)
                {
                    buttonLuu.IsEnabled = true;
                }
            }
            else
            {
                danhapchuoi = false;
                buttonLuu.IsEnabled = false;
            }
        }

        private void buttonLuu_Click(object sender, RoutedEventArgs e)
        {
            buttonLuu.IsEnabled = false;
            textBoxChuoi.IsEnabled = false;
            textBoxSo.IsEnabled = false;
            chuoi = textBoxChuoi.Text;
        }

        private void textBoxXuat_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                buttonXuat.IsEnabled = true;
            }
            else
            {
                buttonXuat.IsEnabled = false;
            }
        }

        private void buttonXuat_Click(object sender, RoutedEventArgs e)
        {
            bool ok = true;
            foreach (Char c in textBoxXuat.Text)
            {
                if (!Char.IsDigit(c))
                {
                    ok = false;
                }
            }
            if (ok == true)
            {
                if (textBoxSo.Text == textBoxXuat.Text)
                {
                    textBoxXuatChu.Text = textBoxChuoi.Text;
                }
                else
                {
                    textBoxXuatChu.Text = "";
                }
            }
            else
            {
                textBoxXuatChu.Text = "";
            }
        }
    }
}

<Window x:Class="WpfApplication6.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Grid>
        <Button Content="Nhập" Height="23" HorizontalAlignment="Left" Margin="215,38,0,0" Name="buttonNhap" VerticalAlignment="Top" Width="75" Click="buttonNhap_Click" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="36,38,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" TextChanged="textBox1_TextChanged" />
        <ComboBox Height="23" HorizontalAlignment="Left" Margin="340,38,0,0" Name="comboBox1" VerticalAlignment="Top" Width="120" />
    </Grid>
</Window>

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.Navigation;
using System.Windows.Shapes;

namespace WpfApplication6
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            buttonNhap.IsEnabled = false;
        }

        private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                if (Char.IsDigit(c) || Char.IsControl(c)) newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                buttonNhap.IsEnabled = true;
            }
            else
            {
                buttonNhap.IsEnabled = false;
            }
        }

        private void buttonNhap_Click(object sender, RoutedEventArgs e)
        {
            comboBox1.Items.Add(textBox1.Text.Trim());
            buttonNhap.IsEnabled = false;
            textBox1.Text = "";
        }
    }
}

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.Navigation;
using System.Windows.Shapes;

namespace WpfApplication8
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        bool so1 = false;
        bool so2 = false;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void textBoxSo1_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                if (Char.IsDigit(c) || Char.IsControl(c)) newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                so1 = true;
                if (so2 == true)
                {
                    buttonBang.IsEnabled = buttonBeHon.IsEnabled = buttonLonHon.IsEnabled = true;
                }
            }
            else
            {
                so1 = false;
                buttonBang.IsEnabled = buttonBeHon.IsEnabled = buttonLonHon.IsEnabled = false;
            }
        }

        private void textBoxSo2_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            Int32 selectionStart = textBox.SelectionStart;
            Int32 selectionLength = textBox.SelectionLength;

            String newText = String.Empty;
            foreach (Char c in textBox.Text.ToCharArray())
            {
                if (Char.IsDigit(c) || Char.IsControl(c)) newText += c;
            }

            textBox.Text = newText;

            textBox.SelectionStart = selectionStart <= textBox.Text.Length ?
            selectionStart : textBox.Text.Length;

            if (textBox.Text.Length != 0)
            {
                so2 = true;
                if (so1 == true)
                {
                    buttonBang.IsEnabled = buttonBeHon.IsEnabled = buttonLonHon.IsEnabled = true;
                }
            }
            else
            {
                so2 = false;
                buttonBang.IsEnabled = buttonBeHon.IsEnabled = buttonLonHon.IsEnabled = false;
            }
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            buttonBang.IsEnabled = buttonBeHon.IsEnabled = buttonLonHon.IsEnabled = false;
        }

        private void buttonBang_Click(object sender, RoutedEventArgs e)
        {
            int mot = int.Parse(textBoxSo1.Text.Trim());
            int hai = int.Parse(textBoxSo2.Text.Trim());
            if (mot == hai)
            {
                MessageBox.Show("Bang Nhau!");
            }
            else
            {
                MessageBox.Show("Khong Bang Nhau!");
            }
        }

        private void buttonLonHon_Click(object sender, RoutedEventArgs e)
        {
            int mot = int.Parse(textBoxSo1.Text.Trim());
            int hai = int.Parse(textBoxSo2.Text.Trim());
            if (mot > hai)
            {
                MessageBox.Show("So 1 Lon Hon So 2!");
            }
            else
            {
                MessageBox.Show("So 1 Khong Lon Hon So 2!");
            }
        }

        private void buttonBeHon_Click(object sender, RoutedEventArgs e)
        {
            int mot = int.Parse(textBoxSo1.Text.Trim());
            int hai = int.Parse(textBoxSo2.Text.Trim());
            if (mot < hai)
            {
                MessageBox.Show("So 1 Be Hon So 2!");
            }
            else
            {
                MessageBox.Show("So 1 Khong Be Hon So 2!");
            }
        }
    }
}