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+---
+title: L2DBForm.xaml.cs source code
+ms.date: 10/22/2019
+ms.topic: sample
+---
+# L2DBForm.xaml.cs source code
+
+This page contains the contents and description of the C# source code in the file *L2DBForm.xaml.cs*. The L2XDBForm partial class contained in this file can be divided into three logical sections: data members and the `OnRemove` and `OnAddBook` button click event handlers.
+
+## Data members
+
+Two private data members are used to associate this class to the window resources used in *L2DBForm.xaml*.
+
+- The namespace variable `myBooks` is initialized to `"http://www.mybooks.com"`.
+
+- The member `bookList` is initialized in the constructor to the CDATA string in *L2DBForm.xaml* with the following line:
+
+    ```csharp
+    bookList = (XElement)((ObjectDataProvider)Resources["LoadedBooks"]).Data;
+    ```
+
+## OnAddBook event handler
+
+This method contains the following three statements:
+
+- The first conditional statement is used for input validation.
+
+- The second statement creates a new <xref:System.Xml.Linq.XElement> from the string values the user entered in the **Add New Book** user interface (UI) section.
+
+- The last statement adds this new book element to the data provider in *L2DBForm.xaml*. Consequently, dynamic data binding will automatically update the UI with this new item; no extra user-supplied code is required.
+
+## OnRemove event handler
+
+The `OnRemove` handler is more complicated than the `OnAddBook` handler for two reasons. First, because the raw XML contains preserved white space, matching newlines must also be removed with the book entry. Second, as a convenience, the selection, which was on the deleted item, is reset to the previous one in the list.
+
+However, the core work of removing the selected book item is accomplished by only two statements:
+
+- First, the book element associated with the currently selected item in the list box is retrieved:
+
+    ```csharp
+    XElement selBook = (XElement)lbBooks.SelectedItem;
+    ```
+
+- Then, this element is deleted from the data provider:
+
+    ```csharp
+    selBook.Remove();
+    ```
+
+Again, dynamic data binding assures that the program's UI is automatically updated.
+
+## Example
+
+### Code
+
+```csharp
+using System;
+using System.Linq;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Input;
+using System.Xml;
+using System.Xml.Linq;
+
+namespace LinqToXmlDataBinding {
+    /// <summary>
+    /// Interaction logic for L2XDBForm.xaml
+    /// </summary>
+
+    public partial class L2XDBForm : System.Windows.Window
+    {
+        XNamespace mybooks = "http://www.mybooks.com";
+        XElement bookList;
+
+        public L2XDBForm()
+        {
+            InitializeComponent();
+            bookList = (XElement)((ObjectDataProvider)Resources["LoadedBooks"]).Data;
+        }
+
+        void OnRemoveBook(object sender, EventArgs e)
+        {
+            int index = lbBooks.SelectedIndex;
+            if (index < 0) return;
+
+            XElement selBook = (XElement)lbBooks.SelectedItem;
+            //Get next node before removing element.
+            XNode nextNode = selBook.NextNode;
+            selBook.Remove();
+
+            //Remove any matching newline node.
+            if (nextNode != null && nextNode.ToString().Trim().Equals(""))
+            { nextNode.Remove(); }
+
+            //Set selected item.
+            if (lbBooks.Items.Count > 0)
+            {  lbBooks.SelectedItem = lbBooks.Items[index > 0 ? index - 1 : 0]; }
+        }
+
+        void OnAddBook(object sender, EventArgs e)
+        {
+            if (String.IsNullOrEmpty(tbAddID.Text) ||
+                String.IsNullOrEmpty(tbAddValue.Text))
+            {
+                MessageBox.Show("Please supply both a Book ID and a Value!", "Entry Error!");
+                return;
+            }
+            XElement newBook = new XElement(
+                                mybooks + "book",
+                                new XAttribute("id", tbAddID.Text),
+                                tbAddValue.Text);
+            bookList.Add("  ", newBook, "\r\n");
+        }
+    }
+}
+```
+
+### Comments
+
+For the associated XAML source for these handlers, see [L2DBForm.xaml source code](l2dbform-xaml-source-code.md).
+
+## See also
+
+- [Walkthrough: LinqToXmlDataBinding example](linq-to-xml-data-binding-sample.md)
+- [L2DBForm.xaml source code](l2dbform-xaml-source-code.md)