Add new create wpf app article (#193)

dotnet-desktop-guide/net/wpf/get-started/snippets/create-app-visual-studio/csharp/Final.xaml.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+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 Names
+{
+    /// <summary>
+    /// Interaction logic for Final.xaml
+    /// </summary>
+    public partial class Final : Window
+    {
+        public Final()
+        {
+            InitializeComponent();
+        }
+
+        //<FinalCode>
+        private void ButtonAddName_Click(object sender, RoutedEventArgs e)
+        {
+            if (!string.IsNullOrWhiteSpace(txtName.Text) && !lstNames.Items.Contains(txtName.Text))
+                lstNames.Items.Add(txtName.Text);
+        }
+        //</FinalCode>
+    }
+}