XML Attributes

	XML Attributes

Introduction

One of XML strengths is its ability to describe data with various options, using simple or complex elements. Although an element can have a value as large as a long paragraph of text, an element can have only one value. There are cases where you would like the same element to be equipped with, or be able to provide, various values that can also be easily distinguished or separate. To provide various types of information to an XML element, you can use one or more attributes

Creating an Attribute

In C++, we are used to creating classes. Imagine that you want to create one for employees. Such a class would appear as follows:

// This is the main project file for VC++ application project 
// generated using an Application Wizard.

#include "stdafx.h"

#using <mscorlib.dll>

using namespace std;
using namespace System;

__value struct CEmployeeRecord
{
	String   *Username;
	String   *Password;
	Double    Salary;
	__wchar_t MaritalStatus;
};

int _tmain()
{
    	// TODO: Please replace the sample code below with your own.
	CEmployeeRecord emplRecord;

	emplRecord.Username = S"kallar";
	emplRecord.Password = S"7hd47D89";
	emplRecord.Salary   = 20.12;
	emplRecord.MaritalStatus = L'D';

	Console::WriteLine(S"Username:       {0}", emplRecord.Username);
	Console::WriteLine(S"Password:       {0}", emplRecord.Password);
	Console::WriteLine(S"Marital Status: {0}", __box(emplRecord.MaritalStatus));
	Console::WriteLine(S"Hourly  Salary: {0}", __box(emplRecord.Salary));

    	Console::WriteLine();
	return 0;
}

This would produce:

Username:       kallar
Password:       7hd47D89
Marital Status: D
Hourly  Salary: 20.12

Press any key to continue

The members of such a class are said to describe the class. When you instantiate the class (when you declare a variable of that class), you can provide value for one or more member variables. Another instance of the class can have different values.

In XML, a tag is like a variable of a C++ class, except that you don't have to create the class but you must create the tag. Inside of the start tag, you can provide one or more attributes that mimic the member variables of a class.

An attribute is created in the start tag using the formula:

<tag Attribute_Name="Value">Element_Value</tag>

Like the tag, the name of an attribute is up to you. On the right side of the attribute, type its value in double-quotes. The end tag doesn't need any information about any attribute. It is only used to close the tag. Here is an example of a tag that uses an attribute:

<salary status="Full Time">22.05</salary >

In this example, status="Full Time" is called an attribute of the salary element.

One of the good features of an attribute is that it can carry the same type of value as that of an XML tag. Therefore, using an attribute, you can omit giving a value to a tag. For example, instead of creating the following tag with its value:

<movie>Coming to America</movie>

You can use an attribute to carry the value of the tag. Here is an example:

<movie title="Coming to America"></movie>

In this case, you can still provide another or new value for the tag.

You can create more than one attribute in a tag. To do this, separate them with an empty space. Here is an example:

<movie title="Coming to America" director="John Landis" length="116 min">Nile Rodgers</movie>

If you create a tag that uniquely contains attributes without a formal value, you can omit the end tag. In this case, you can close the start tag as you would do for an empty tag. Here is an example:

<movie title="Coming to America" />

Practical Learning: Creating XML Attributes

If you want to apply an example, start Microsoft Visual C++ .NET and create a new Windows Forms Application named DepartmentStore1
To create a new XML file, on the main menu, click Project -> Add New Item...
In the Templates section, click XML File (.xml)
In the Name text box, type Inventory and press Enter

Complete the file as follows:

<?xml version="1.0" encoding="utf-8"?>
<StoreItems>
  <Item ItemNumber="947783" ItemDescription="Double-faced wool coat" UnitPrice="275.25" />
  <Item ItemNumber="934687" ItemDescription="Floral Silk Tank Blouse" UnitPrice="180.00" />
  <Item ItemNumber="973947" ItemDescription="Push Up Bra" UnitPrice="50.00" />
  <Item ItemNumber="987598" ItemDescription="Chiffon Blouse" UnitPrice="265.00" />
  <Item ItemNumber="974937" ItemDescription="Bow Belt Skirtsuit" UnitPrice="245.55" />
  <Item ItemNumber="743765" ItemDescription="Cable-knit Sweater" UnitPrice="45.55" />
  <Item ItemNumber="747635" ItemDescription="Jeans with Heart Belt" UnitPrice="25.65" />
  <Item ItemNumber="765473" ItemDescription="Fashionable mini skirt" UnitPrice="34.55" />
  <Item ItemNumber="754026" ItemDescription="Double Dry Pants" UnitPrice="28.55" />
  <Item ItemNumber="730302" ItemDescription="Romantic Flower Dress" UnitPrice="24.95" />
  <Item ItemNumber="209579" ItemDescription="Cotton Polo Shirt" UnitPrice="45.75" />
  <Item ItemNumber="267583" ItemDescription="Pure Wool Cap" UnitPrice="25.00" />
  <Item ItemNumber="248937" ItemDescription="Striped Cotton Shirt" UnitPrice="65.55" />
  <Item ItemNumber="276057" ItemDescription="Two-Toned Ribbed Crewneck" UnitPrice="9.75" />
  <Item ItemNumber="267945" ItemDescription="Chestnut Italian Shoes" UnitPrice="165.75" />
  <Item ItemNumber="409579" ItemDescription="Under Collar and Placket Jacket" UnitPrice="265.15" />
  <Item ItemNumber="467583" ItemDescription="Country Coat Rugged Wear" UnitPrice="35.55" />
  <Item ItemNumber="448937" ItemDescription="Carpenter Jeans" UnitPrice="24.95" />
  <Item ItemNumber="476057" ItemDescription="Double-Cushion Tennis Shoes" UnitPrice="48.75" />
  <Item ItemNumber="467945" ItemDescription="Stitched Center-Bar Belt" UnitPrice="32.50" />					 
</StoreItems>

On the main menu, click Project -> Add New Item...
To add another form, in the Templates list, click Window Form (.NET)
Set the Name to Inventory
Press Enter

Design the form as follows:

Sandrine Hoaks Department Store - Inventory

Control	Name	Text	Additional Properties
DataGrid			AutoFormat: Colorful 3 Anchor: Top, Bottom, Left, Right BorderStyle: Fixed3D CaptionText: Store Inventory
Button	btnLoad	&Load	Anchor: Bottom, Left
Button	btnClose	&Close	Anchor: Bottom, Right

From the Data section of the Toolbox, click a DataSet and click the form
In the Add Dataset dialog box, click the Untyped Dataset radio button
Click OK

Double-click the Load button and implement its event as follows:

private: System::Void btnLoad_Click(System::Object *  sender, System::EventArgs *  e)
{
	 this->dataSet1->ReadXml(S"Inventory.xml");

	 this->dataGrid1->DataSource = this->dataSet1;
	 this->dataGrid1->DataMember = S"Item";
}

Return to the Inventory form. Double-click the Close button and implement its event as follows:

private: System::Void btnClose_Click(System::Object *  sender, System::EventArgs *  e)
{
	 Close();
}

Display the first form by clicking the Form1.h [Design] tab
Add a button to it and set its properties as follows:
Name: btnInventory
Text: &View Inventory

Double-click the new button and implement its Click event as follows:

#pragma once

#include "Inventory.h"

namespace DepartmentStore1
{
	using namespace System;
	using namespace System::ComponentModel;
	using namespace System::Collections;
	using namespace System::Windows::Forms;
	using namespace System::Data;
	using namespace System::Drawing;

	. . . No Change
			
private: System::Void btnInventory_Click(System::Object *  sender, System::EventArgs *  e)
		{
			 Inventory *frm = new Inventory;
			 frm->ShowDialog();
		}

	};
}

Test the application
Close the form
On the main menu, click Project -> Add New Item...
To add another form, in the Templates list, click Window Form (.NET)
Set the Name to OrderProcessing and press Enter

Design the form as follows:

Control	Name	Text	Additional Properties
Label		Item #
Label		Description
Label		Unit Price
Label		Qty
Label		Sub Total
TextBox	txtPartID1
TextBox	txtDescription1
TextBox	txtUnitPrice1	0.00	TextAlign: Right
TextBox	txtQuantity1	0	TextAlign: Right
TextBox	txtSubTotal1	0.00	TextAlign: Right
TextBox	txtPartID2
TextBox	txtDescription2
TextBox	txtUnitPrice2	0.00	TextAlign: Right
TextBox	txtQuantity2	0	TextAlign: Right
TextBox	txtSubTotal2	0.00	TextAlign: Right
TextBox	txtPartID3
TextBox	txtDescription3
TextBox	txtUnitPrice3	0.00	TextAlign: Right
TextBox	txtQuantity3	0	TextAlign: Right
TextBox	txtSubTotal3	0.00	TextAlign: Right
TextBox	txtPartID4
TextBox	txtDescription4
TextBox	txtUnitPrice4	0.00	TextAlign: Right
TextBox	txtQuantity4	0	TextAlign: Right
TextBox	txtSubTotal4	0.00	TextAlign: Right
TextBox	txtPartID5
TextBox	txtDescription5
TextBox	txtUnitPrice5	0.00	TextAlign: Right
TextBox	txtQuantity5	0	TextAlign: Right
TextBox	txtSubTotal5	0.00	TextAlign: Right
TextBox	txtPartID6
TextBox	txtDescription6
TextBox	txtUnitPrice6	0.00	TextAlign: Right
TextBox	txtQuantity6	0	TextAlign: Right
TextBox	txtSubTotal6	0.00	TextAlign: Right
TextBox	txtPartID7
TextBox	txtDescription7
TextBox	txtUnitPrice7	0.00	TextAlign: Right
TextBox	txtQuantity7	0	TextAlign: Right
TextBox	txtSubTotal7	0.00	TextAlign: Right
TextBox	txtPartID8
TextBox	txtDescription8
TextBox	txtUnitPrice8	0.00	TextAlign: Right
TextBox	txtQuantity8	0	TextAlign: Right
TextBox	txtSubTotal8	0.00	TextAlign: Right
Button	btnClose	&Close
Label		&Order Total:
TextBox	txtTotalOrder

On the form, click the first text box under Item #
In the Properties window, click the Events button and double-click the Leave field
Return to the form and generate the Leave event of each text box under Item #

Implement the Leave events as follows:

private: System::Void txtPartID1_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID1->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");

			 if( partNo->Equals(partID) )
			 {
				 this->txtDecription1->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice1->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity1->Text = S"1";
				 this->txtSubTotal1->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity1->Focus();
			 }
			 break;
		 }
	 }
}

private: System::Void txtPartID2_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID2->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription2->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice2->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity2->Text = S"1";
				 this->txtSubTotal2->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity2->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID3_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID3->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription3->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice3->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity3->Text = S"1";
				 this->txtSubTotal3->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity3->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID4_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID4->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription4->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice4->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity4->Text = S"1";
				 this->txtSubTotal4->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity4->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID5_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID5->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription5->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice5->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity5->Text = S"1";
				 this->txtSubTotal5->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity5->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID6_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID6->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription6->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice6->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity6->Text = S"1";
				 this->txtSubTotal6->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity6->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID7_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID7->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription7->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice7->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity7->Text = S"1";
				 this->txtSubTotal7->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity7->Focus();
			 }
			break;
		}
	}
}

private: System::Void txtPartID8_Leave(System::Object *  sender, System::EventArgs *  e)
{
	 String *partNo = this->txtPartID8->Text;
	 String *partID = 0;

	 XmlTextReader *xtr = new XmlTextReader(S"Inventory.xml");

	 while(xtr->Read())
	 {
		 switch(xtr->NodeType)
		 {
		 case XmlNodeType::Element:
			 partID = xtr->GetAttribute(S"ItemNumber");
			 if( partNo->Equals(partID) )
			 {
				 this->txtDescription8->Text = xtr->GetAttribute(S"ItemDescription");
				 this->txtUnitPrice8->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity8->Text = S"1";
				 this->txtSubTotal8->Text = xtr->GetAttribute(S"UnitPrice");
				 this->txtQuantity8->Focus();
			 }
			break;
		}
	}
}

In the top section of the Code Editor, under the other using namespace line add using namespace System::Xml

In the Code Editor, define a method as follows:

void CalculateTotal(void)
{
	double subTotal1 = this->txtSubTotal1->Text->ToDouble(0);
	double subTotal2 = this->txtSubTotal2->Text->ToDouble(0);
	double subTotal3 = this->txtSubTotal3->Text->ToDouble(0);
	double subTotal4 = this->txtSubTotal4->Text->ToDouble(0);
	double subTotal5 = this->txtSubTotal5->Text->ToDouble(0);
	double subTotal6 = this->txtSubTotal6->Text->ToDouble(0);
	double subTotal7 = this->txtSubTotal7->Text->ToDouble(0);
	double subTotal8 = this->txtSubTotal8->Text->ToDouble(0);
	double totalOrder = subTotal1 + subTotal2 + subTotal3 + subTotal4 +
			subTotal5 + subTotal6 + subTotal7 + subTotal8;

	this->txtTotalOrder->Text = totalOrder.ToString(S"F");
}

On the form, click the first text box under Qty
In the Properties window, double-click the Leave field
Return to the form and generate the Leave event of each text box under Qty

Implement the Leave events as follows:

private: System::Void txtQuantity1_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice1->Text->ToDouble(0);
			 int qty = this->txtQuantity1->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal1->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity2_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice2->Text->ToDouble(0);
			 int qty = this->txtQuantity2->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal2->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity3_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice3->Text->ToDouble(0);
			 int qty = this->txtQuantity3->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal3->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity4_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice4->Text->ToDouble(0);
			 int qty = this->txtQuantity4->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal4->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity5_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice5->Text->ToDouble(0);
			 int qty = this->txtQuantity5->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal5->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity6_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice6->Text->ToDouble(0);
			 int qty = this->txtQuantity6->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal6->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity7_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice7->Text->ToDouble(0);
			 int qty = this->txtQuantity7->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal7->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

private: System::Void txtQuantity8_Leave(System::Object *  sender, System::EventArgs *  e)
		 {
			 double unitPrice = this->txtUnitPrice8->Text->ToDouble(0);
			 int qty = this->txtQuantity8->Text->ToInt16(0);
			 double subTotal = unitPrice * qty;

			 this->txtSubTotal8->Text = subTotal.ToString(S"F");
			 CalculateTotal();
		 }

On the form, double-click the Close button and implement its Click event as follows:

private: System::Void button2_Click(System::Object *  sender, System::EventArgs *  e)
{
	 Close();
}

Display the first form by clicking the Form1.h [Design] tab
Add a button to it and set its properties as follows:
Name: btnOrders
Text: &Order Processing

Double-click the new button and implement its Click event as follows:

#pragma once

#include "Inventory.h"
#include "OrderProcessing.h"

namespace DepartmentStore1
{
	. . . No Change


	private: System::Void btnOrders_Click(System::Object *  sender, System::EventArgs *  e)
			 {
				 OrderProcessing *frm = new OrderProcessing;
				 frm->ShowDialog();
			 }

	};
}

Return to the form and add a button to it
Set its properties as follows:
Name: btnClose
Text: &Close

Double-click the new button and implement its Click event as follows:

private: System::Void btnClose_Click(System::Object *  sender, System::EventArgs *  e)
{
	 Close();
}

Execute the application
After using it, close the form


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