This C# program demonstrates how to create a simple button and a handle a click event in a WPF program.

MainWindow.xaml

<Window x:Class="Button.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>
        <TextBlock Name="qTextBlock" HorizontalAlignment="Left" Margin="10,10,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top"/>
        <Button Content="Button" HorizontalAlignment="Left" Margin="10,31,0,0" VerticalAlignment="Top" Width="75"  Click="OnButtonClick"/>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace Button {
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
        }
        private void OnButtonClick(object sender, RoutedEventArgs e) {
            qTextBlock.Text = "Button Clicked";
        }
    }
}

Window with Button

Button Clicked