/// <summary>
/// Method to update an existing book in the catalog.
/// Defines the implementation of the PUT method.
/// </summary>
public BookDetails UpdateBook(String id, BookDetails book)
{
try
{
// Retrieve a specific book from the catalog.
XElement updateBook = xmlDocument.XPathSelectElement(String.Format("catalog/book[@id='{0}']", id));
// Verify that the book exists.
if (updateBook != null)
{
// Create elements for each of the book's data items.
XElement[] bookInfo = FormatBookData(book);
// Add the element to the book element.
updateBook.ReplaceNodes(bookInfo);
// Save the XML document.
xmlDocument.Save(xmlFilename);
// Return an object for the updated book.
return this.ReadBook(id);
}
}
catch (Exception ex)
{
// Rethrow the exception.
throw ex;
}
// Return null to signify failure.
return null;
}
/// <summary>
/// Populates a book BookDetails class with the data for a book.
/// </summary>
private XElement[] FormatBookData(BookDetails book)
{
XElement[] bookInfo =
{
new XElement("author", book.Author),
new XElement("title", book.Title),
new XElement("genre", book.Genre),
new XElement("price", book.Price.ToString()),
new XElement("publish_date", book.PublishDate.ToString()),
new XElement("description", book.Description)
};
return bookInfo;
}
/// <summary>
/// Method to add a new book to the catalog.
/// Defines the implementation of the POST method.
/// </summary>
public BookDetails CreateBook(BookDetails book)
{
try
{
// Retrieve the book with the highest ID from the catalog.
var highestBook = (
from bookNode in xmlDocument.Elements("catalog").Elements("book")
orderby bookNode.Attribute("id").Value descending
select bookNode).Take(1);
// Extract the ID from the book data.
string highestId = highestBook.Attributes("id").First().Value;
// Create an ID for the new book.
string newId = "bk" + (Convert.ToInt32(highestId.Substring(2)) + 1).ToString();
// Verify that this book ID does not currently exist.
if (this.ReadBook(newId) == null)
{
// Retrieve the parent element for the book catalog.
XElement bookCatalogRoot = xmlDocument.Elements("catalog").Single();
// Create a new book element.
XElement newBook = new XElement("book", new XAttribute("id", newId));
// Create elements for each of the book's data items.
XElement[] bookInfo = FormatBookData(book);
// Add the element to the book element.
newBook.ReplaceNodes(bookInfo);
// Append the new book to the XML document.
bookCatalogRoot.Add(newBook);
// Save the XML document.
xmlDocument.Save(xmlFilename);
// Return an object for the newly-added book.
return this.ReadBook(newId);
}
}
catch (Exception ex)
{
// Rethrow the exception.
throw ex;
}
// Return null to signify failure.
return null;
}
