Please Answer in C#

Extra $15-1$ Create and use an interface

In this exercise, you'll create an IDisplayable interface and then use it in the

InventoryItem class of the Inventory Maintenance app.

Open the InventoryMaintenance project in the ExtraStarts $\frac{\frac{?}{?}}{C}h\frac{15}{\frac{?}{?}}$

InventoryMaintIDisplayable directory.

Create a public interface named IDisplayable. Then, add the declaration for a

method named GetDisplayText$()$ with no parameters and a string return value.

Display the code for the InventoryItem class, find the GetDisplayText$()$ method

that this class contains, and comment out this method.

Modify the declaration for the class to indicate that it implements the

IDisplayable interface. Then, generate a stub for the GetDisplayText$()$ method

that this interface defines.

Modify the declaration for the GetDisplayText$()$ method so it can be overridden.

Then, replace the generated code for this method with the code in the original

GetDisplayText$()$ method that you commented out in step $3.$

Test the app to be sure it still works.

Display the code for the Inventory Maintenance form. In the FillItemListBox$()$

method, change the type of the item variable from InventoryItem to IDisplayable.

Test the app to be sure it still works.

Modify the event handler for the Click event of the Add button to include the

following debugging code after the code that gets an InventoryItem object named

item from the New Item form:

Debug.Writeline $($$"Item type: $\{$item$.$GetType $()\}")$;

Debug.WriteLine$($$"Item is InventoryItem: $\{$item is InventoryItem$\}")$;

Debug.WriteLine$($$"Item is IDisplayable: $\{$item is IDisplayable$\}")$;

Run the app and add a new Plant item and a new Supply item. After adding each

item, check the Output window and review the information that's displayed.

This is the code I have so Far:

namespace InventoryMaintenance

$\{$

public partial class frmNewItem : Form

$\{$

public frmNewItem$()$

$\{$

InitializeComponent$()$;

$\}$

private InventoryItem item $=$ null!;

public InventoryItem GetNewItem$()$

$\{$

rdoPlant.Checked $=$ true;

this.ShowDialog$()$;

return item;

$\}$

private void btnSave$\_$Click$($object sender$,$ EventArgs e$)$

$\{$

if $($IsValidData$())$

$\{$

if $($rdoPlant$.$Checked$)$

$\{$

item $=$ new Plant$($

Convert.ToInt$32($txtItemNo$.$Text$),$

txtDescription.Text,

Convert.ToDecimal$($txtPrice$.$Text$),$

cboSizeOrManufacturer.SelectedItem.ToString$()!$

$)$;

$\}$

else

$\{$

item $=$ new Supply$($

Convert.ToInt$32($txtItemNo$.$Text$),$

txtDescription.Text,

Convert.ToDecimal$($txtPrice$.$Text$),$

cboSizeOrManufacturer.SelectedItem.ToString$()!$

$)$;

$\}$

this.Close$()$;

$\}$

$\}$

private bool IsValidData$()$

$\{$

bool success $=$ true;

string errorMessage $=""$;

errorMessage $+=$ Validator.IsPresent$($txtItemNo$.$Text, "Item no$")$;

errorMessage $+=$ Validator.IsInt$32($txtItemNo$.$Text, "Item no$")$;

errorMessage $+=$ Validator.IsPresent$($txtDescription$.$Text, "Description"$)$;

errorMessage $+=$ Validator.IsPresent$($txtPrice$.$Text, "Price"$)$;

errorMessage $+=$ Validator.IsDecimal$($txtPrice$.$Text, "Price"$)$;

$//$ Validate combo box $-$ use label text for name $-$ remove ending colon

string name $=$ lblSizeOrManufacturer.Text.Substring$(0,$ lblSizeOrManufacturer.Text.Length $-1)$;

errorMessage $+=$ Validator.IsSelected$($cboSizeOrManufacturer$.$SelectedIndex, name$)$;

if $($errorMessage $!="")$

$\{$

success $=$ false;

MessageBox.Show$($errorMessage$,$ "Entry Error"$)$;

$\}$

return success;

$\}$

private void rdoPlant$\_$CheckedChanged$($object sender$,$ EventArgs e$)$

$\{$

if $($rdoPlant$.$Checked$)$

lblSizeOrManufacturer.Text $=$ "Size:";

else

lblSizeOrManufacturer.Text $=$ "Manufacturer:";

LoadComboBox$()$;

$\}$

private void LoadComboBox$()$

$\{$

cboSizeOrManufacturer.Items.Clear$()$;

if $($rdoPlant$.$Checked$)$

$\{$

cboSizeOrManufacturer.Items.Add$("1$ gallon"$)$;

cboSizeOrManufacturer.Items.Add$("5$ gallon"$)$;

cboSizeOrManufacturer.Items.Add$("15$ gallon"$)$;

cboSizeOrManufacturer.Items.Add$("24-$inch box"$)$;

cboSizeOrManufacturer.Items.Add$("36-$inch box"$)$;

$\}$

else

$\{$

cboSizeOrManufacturer.Items.Add$("$Bayer$")$;