Add a class named InvItem to this project, and add the properties, method, and constructors that are shown in the table above.

Add code to implement the New Item form

Display the code for the New Item form and declare a class$-$level InvItem variable named invItem with an initial value of null.

Add a public method named GetNewItem$()$ that displays the form as a dialog box and returns an InvItem object.

Add code to the btnSave$\_$Click$()$ event handler that creates a new InvItem object and closes the form if the data is valid. Add code to implement the Inventory Maintenance form

Display the code for the Inventory Maintenance form and declare a class$-$level List variable named invItems with an initial value of null.

Add a statement to the frmInvMaint$\_$Load$()$ event handler that uses the GetItems$()$ method of the InvItemDB class to load the items list.

Add code to the FillItemListBox$()$ method that adds the items in the list to the Items list box. Use the GetDisplayText$()$ method of the InvItem class to format the item data.

Add code to the btnAdd$\_$Click$()$ event handler that creates a new instance of the New Item form and executes the GetNewItem$()$ method of that form. If the InvItem object that$$s returned by this method is not null, this event handler should add the new item to the list, call the SaveItems$()$ method of the InvItemDB class to save the list, and then refresh the Items list box. Test the application to be sure this event handler works.

Add code to the btnDelete$\_$Click$()$ event handler that removes the selected item from the list, calls the SaveItems$()$ method of the InvItemDB class to save the list, and refreshes the Items list box. Be sure to confirm the delete operation. Then, test the application to be sure this event handler works.

$**************$InvItemDB$.$cs

using System;

using System.Collections.Generic;

using System.Text;

using System.Xml;

namespace InventoryMaintenance

$\{$

public static class InvItemDB

$\{$

private const string Path $=$ @"InventoryItems.xml$"$;

public static List GetItems$()$

$\{$

$//$ create the list

List items $=$ new List$()$;

$//$ create the XmlReaderSettings object

XmlReaderSettings settings $=$ new XmlReaderSettings$()$;

settings.IgnoreWhitespace $=$ true;

settings.IgnoreComments $=$ true;

$//$ create the XmlReader object

XmlReader xmlIn $=$ XmlReader.Create$($Path$,$ settings$)$;

$//$ read past all nodes to the first Book node

if $($xmlIn$.$ReadToDescendant$("$Item$"))$

$\{$

$//$ create one Product object for each Product node

do

$\{$

InvItem item $=$ new InvItem$()$;

xmlIn.ReadStartElement$("$Item$")$;

item.ItemNo $=$ xmlIn.ReadElementContentAsInt$()$;

item.Description $=$ xmlIn.ReadElementContentAsString$()$;

item.Price $=$ xmlIn.ReadElementContentAsDecimal$()$;

items.Add$($item$)$;

$\}$

while $($xmlIn$.$ReadToNextSibling$("$Item$"))$;

$\}$

$//$ close the XmlReader object

xmlIn.Close$()$;

return items;

$\}$

public static void SaveItems$($List items$)$

$\{$

$//$ create the XmlWriterSettings object

XmlWriterSettings settings $=$ new XmlWriterSettings$()$;

settings.Indent $=$ true;

settings.IndentChars $=("")$;

$//$ create the XmlWriter object

XmlWriter xmlOut $=$ XmlWriter.Create$($Path$,$ settings$)$;

$//$ write the start of the document

xmlOut.WriteStartDocument$()$;

xmlOut.WriteStartElement$("$Items$")$;

$//$ write each product object to the xml file

foreach $($InvItem item in items$)$

$\{$

xmlOut.WriteStartElement$("$Item$")$;

xmlOut.WriteElementString$("$ItemNo$",$ Convert.ToString$($item$.$ItemNo$))$;

xmlOut.WriteElementString$("$Description$",$ item.Description$)$;

xmlOut.WriteElementString$("$Price$",$ Convert.ToString$($item$.$Price$))$;

xmlOut.WriteEndElement$()$;

$\}$

$//$ write the end tag for the root element

xmlOut.WriteEndElement$()$;

$//$ close the xmlWriter object

xmlOut.Close$()$;

$\}$

$\}$

$\}$

$********$Program$.$cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace InventoryMaintenance

$\{$

static class Program

$\{$

$///$