XML-Based Applications: College Park Auto-Parts

	XML-Based Applications: College Park Auto-Parts

Inventory Creation

The inventory of our store is created by adding store items to an XML file. To do this, once again, we take advantage of the XmlDocument, the XmlNode, and its derived classes. This inventory is created using the New Part form.

We need to apply some rules in order to create a store item. Early rules can make the application easier to use and maintain. For example, we must create an item only if it can be clearly identified. This makes it easy to locate it when processing an order. We explain through the comments in the code.

Practical Learning: Creating the Inventory

Display the New Model form and double-click the New Make button

Change the Click event of the btnNewMake button as follows:

System::Void btnNewMake_Click(System::Object *  sender, System::EventArgs *  e)
{
	 // The new car make will come from the New Make dialog box
	 NewMake *frmMake = new NewMake;

	 // Display the New Make dialog box and find out if the user clicked OK
	 if( frmMake->ShowDialog() == DialogResult::OK )
	 {
		 String *strNewMake = frmMake->txtNewMake->Text;

		 // If the user didn't create a new Make, don't do anything
		 if( strNewMake->Equals(S"") )
			 return;

		 // Before adding the new make, check that it doesn't exist already
		 if( this->cboMakes->FindStringExact(strNewMake) > 0 )
			 return;

		 // Now you can add it
		 this->cboMakes->Items->Add(strNewMake);
		 // The user likely wants this new item selected
		 this->cboMakes->Text = strNewMake;

		 // Open the Cars.xml file
		 XmlDocument *docXMLFile = new XmlDocument;
		 docXMLFile->Load(S"Cars.xml");

		 // Get the root node so we can explore its children
		 XmlNode *nodRoot = docXMLFile->DocumentElement;
		 
		 // If the car is not in the list already, create its Make node
	XmlNode *nodNewMake  = docXMLFile->CreateNode(XmlNodeType::Element, S"Make", S"");
		 // Create an attribute for the node
	 dynamic_cast<XmlElement *>(nodNewMake)->SetAttribute(S"MakeName", strNewMake);
		 
		 // Add the new node to the XML file
		 docXMLFile->DocumentElement->AppendChild(nodNewMake);
		 
		 // Save the file
		 docXMLFile->Save(S"Cars.xml");
	}
}

Display the New Part form and double-click the New Make button

Change the Click event of the btnNewMake button as follows:

System::Void btnNewMake_Click(System::Object *  sender, System::EventArgs *  e)
{
	 // The new car make will come from the New Make dialog box
	 NewMake *frmMake = new NewMake;

	 // Display the New Make dialog box and find out if the user clicked OK
	 if( frmMake->ShowDialog() == DialogResult::OK )
	 {
		 String *strNewMake = frmMake->txtNewMake->Text;

		 // If the user didn't create a new Make, don't do anything
		 if( strNewMake->Equals(S"") )
			 return;

		 // Before adding the new make, check that it doesn't exist already
		 if( this->cboMakes->FindStringExact(strNewMake) > 0 )
			 return;

		 // Now you can add it
		 this->cboMakes->Items->Add(strNewMake);
		 // The user likely wants this new item selected
		 this->cboMakes->Text = strNewMake;

		 // Open the Cars.xml file
		 XmlDocument *docXMLFile = new XmlDocument;
		 docXMLFile->Load(S"Cars.xml");

		 // Get the root node so we can explore its children
		 XmlNode *nodRoot = docXMLFile->DocumentElement;
		 
		 // If the car is not in the list already, create its Make node
	XmlNode *nodNewMake  = docXMLFile->CreateNode(XmlNodeType::Element, S"Make", S"");
		 // Create an attribute for the node
	 dynamic_cast<XmlElement *>(nodNewMake)->SetAttribute(S"MakeName", strNewMake);
		 
		 // Add the new node to the XML file
		 docXMLFile->DocumentElement->AppendChild(nodNewMake);
		 
		 // Save the file
		 docXMLFile->Save(S"Cars.xml");
	}
}

Display the New Part form again and double-click the New Model button

Implement its Click event as follows:

System::Void btnNewModel_Click(System::Object *  sender, System::EventArgs *  e)
{
	 // The new car model will come from the New Model dialog box
	 NewModel *frmModel = new NewModel;

	 // Display the New Model dialog box and find out if the user clicked OK
	 if( frmModel->ShowDialog() == DialogResult::OK )
	 {
		 // Retrieve the values that the user specified
		 String *strMake     = frmModel->cboMakes->Text;
		 String *strNewModel = frmModel->txtNewModel->Text;

		 // If the user didn't select a Make, don't do anything
		 if( strMake->Equals(S"") )
			 return;
		 // If the New Model string is empty, don't do anything
		 if( strNewModel->Equals(S"") )
			 return;

		 // Open the Cars.xml file
		 XmlDocument *docXMLFile = new XmlDocument;
		 docXMLFile->Load(S"Cars.xml");

		 // Get the root node so we can explore its children
		 XmlNode *nodRoot     = docXMLFile->DocumentElement;
		 
		 // Create a list of all Make nodes
		 XmlNodeList *lstMakes = docXMLFile->GetElementsByTagName(S"Make");

		 // Visit each Make
		 for(int i = 0; i < lstMakes->Count; i++)
		 {
			 // Get a reference to the current node
			 XmlNode *curMake = lstMakes->ItemOf[i];

			 // If, or when you find the Make
		if( curMake->Attributes->ItemOf[S"MakeName"]->InnerText->Equals(strMake) )
			 {
				 // Since we found the Make, find out if the model exists
				 XmlNodeList *lstCurrentModels = curMake->ChildNodes;

				 // Check each model if the list already contains the model
				 for(int j = 0; j < lstCurrentModels->Count; j++)
				 {
				 if( lstCurrentModels->ItemOf[j]->InnerText->Equals(strNewModel) )
					 {
				MessageBox::Show(S"That model exists already in the database");
						 return;
					 }
				 }

				 // create a child node to it
	    XmlNode *nodModel = docXMLFile->CreateNode(XmlNodeType::Element, S"Model", S"");
			 // Create its value using the string from the New Make dialog box
				 nodModel->InnerText = strNewModel;
				 // Add the new element at the end of the file
				 curMake->AppendChild(nodModel);

				 // Save the file
				 docXMLFile->Save(S"Cars.xml");
				 break;
			 }
		 }
	}
}

Display the New Part form again and double-click the Make combo box

Implement its SelectedIndexChanged event as follows:

System::Void cboMakes_SelectedIndexChanged(System::Object *  sender, System::EventArgs *  e)
{
	 // Empty the Models combo box
	 this->cboModels->Items->Clear();

	 // Find out if the user had selected a Make
	 String *strSelectedMake = this->cboMakes->Text;
	 // Open the Cars.xml file
	 XmlDocument *docXML = new XmlDocument();
	 docXML->Load(S"Cars.xml");

	 // Get a reference to the root node
	 XmlElement *nodRoot = docXML->DocumentElement;
	 // Locate all nodes whose name is Make
	 XmlNodeList *nodMakes = nodRoot->GetElementsByTagName(S"Make");
	 // Look for the Make that is the same the user selected
    	for(int i = 0; i < nodMakes->Count; i++)
	{
	    // Retrieve the value of each Make node and put
String *strMakeName = nodMakes->ItemOf[i]->Attributes->ItemOf[S"MakeName"]->InnerText;
	    // If you find it...
	    if( strMakeName->Equals(strSelectedMake) )
	   {
		// If you find it, make a list of its models...
		XmlNodeList *nodAvailableModels = nodMakes->ItemOf[i]->ChildNodes;
		// ... then add each of its models to the Model combo box
		for(int j = 0; j < nodAvailableModels->Count; j++)
		this->cboModels->Items->Add(nodAvailableModels->ItemOf[j]->InnerText);
	  }
	}
}

Display the New Part form again and double-click the New Category button

Change its Click event as follows:

System::Void btnNewCategory_Click(System::Object *  sender, System::EventArgs *  e)
{
	 // Get a reference to the New Part Category form
	 NewPartCategory *frmCategory = new NewPartCategory;

	 // Display the New Part Category dialog box and find out if the user clicked OK
	 if( frmCategory->ShowDialog() == DialogResult::OK )
	 {
		 String *strCategory = frmCategory->txtNewCategory->Text;

		 // If the user didn't create a new category, don't do anything
		 if( strCategory->Equals(S"") )
			 return;

		 // Before adding the new category, check that it doesn't exist already
		 if( this->cboPartCategories->FindStringExact(strCategory) > 0 )
			 return;

		 // Now you can add it
		 this->cboPartCategories->Items->Add(strCategory);
		 // The user likely wants this new item selected
		 this->cboPartCategories->Text = strCategory;

		 // Open the PartCategories.xml file
		 XmlDocument *docXMLFile = new XmlDocument;
		 docXMLFile->Load(S"PartCategories.xml");

		 // Get the root node so we can explore its children
		 XmlNode *nodRoot = docXMLFile->DocumentElement;
		 
		 // If the new part is not in the list already, create its node
XmlNode *nodNewCategory  = docXMLFile->CreateNode(XmlNodeType::Element, S"PartCategory", S"");
		 // Create text for the node
		 nodNewCategory->InnerText = strCategory;
		 
		 // Add the new node to the XML file
		 docXMLFile->DocumentElement->AppendChild(nodNewCategory);
		 
		 // Save the file
		 docXMLFile->Save(S"PartCategories.xml");
	}
}

Return to the New Part form and double-click the Part Name text box

Implement its TextChanged event as follows:

System::Void txtPartName_TextChanged(System::Object *  sender, System::EventArgs *  e)
{
	 // If there is no part name, no need to add the item to the XML file
	 if( this->txtPartName->Text->Equals(S"") )
		 this->btnAddPart->Enabled = false;
	 else
		 this->btnAddPart->Enabled = true;
}

Return to the New Part form and double-click the Unit Price text box

Implement its TextChanged event as follows:

System::Void txtUnitPrice_TextChanged(System::Object *  sender, System::EventArgs *  e)
{
	 // If the price is not specified, don't add the item to the XML file
	 if( this->txtUnitPrice->Text->Equals(S"") )
		 this->btnAddPart->Enabled = false;
	 else
		 this->btnAddPart->Enabled = true;
}

Return to the New Part form and double-click the Part # text box

Implement its TextChanged event as follows:

System::Void txtPartNumber_TextChanged(System::Object *  sender, System::EventArgs *  e)
{
	 // Make sure that there is a Part Number for this item
	 // Otherwise, don't add the part to the XML file
		 if( this->txtPartNumber->Text->Equals(S"") )
			 this->btnAddPart->Enabled = false;
		 else
			 this->btnAddPart->Enabled = true;
}

Return to the New Part form and double-click the Add Part button

Implement its Click event as follows:

System::Void btnAddPart_Click(System::Object *  sender, System::EventArgs *  e)
{
	 // Open the Parts.xml file
	 XmlDocument *docXML = new XmlDocument();
	 docXML->Load(S"Parts.xml");

	 // Before adding the new part, make sure all components are ready
	 // Otherwise, don't add it
	 if( this->cboYears->SelectedIndex < 0 )
	 {
		 MessageBox::Show(S"You must specify the year. "
				  S"This will help to locate the part");
		 this->cboYears->Focus();
		 return;
	 }
	 if( this->cboMakes->SelectedIndex < 0 )
	 {
		 MessageBox::Show(S"Please select the car make for this part.");
		 this->cboMakes->Focus();
		 return;
	 }
	 if( this->cboModels->SelectedIndex < 0 )
	 {
		 MessageBox::Show(S"The car model is required. "
				S"It helps to know the specific car this part is made for.");
		 this->cboModels->Focus();
		 return;
	 }
	 if( this->txtPartName->Text->Equals(S"") )
	 {
		MessageBox::Show(S"You must specify the part name or a (very) short description.");
		 this->txtPartName->Focus();
		 return;
	 }
	 if( this->txtUnitPrice->Text->Equals(S"") )
	 {
		 MessageBox::Show(S"You must enter the price of each unit of this part.");
		 this->txtUnitPrice->Focus();
		 return;
	 }
	 if( this->txtPartNumber->Text->Equals(S"") )
	 {
		 MessageBox::Show(S"Every item of this database must have a number. "
				  S"The number is just a combination of letters and digits."
				  S"Please make up a number and enter it in the Part # box.");
		 this->txtPartNumber->Focus();
		 return;
	 }

	 // The part seems to be ready
	 // Get a reference to the root node
	 XmlElement *nodNewPart = docXML->CreateElement(S"Part");
	 // Create a new part as a child of the root (this is a simple node addition)
	 String *strNewPart = String::Concat(S"<PartNumber>",
					 this->txtPartNumber->Text, S"</PartNumber>",
					S"<CarYear>", this->cboYears->Text, S"</CarYear>",
					 S"<Make>", this->cboMakes->Text, S"</Make>",
					 S"<Model>", this->cboModels->Text, S"</Model>",
					 S"<PartName Category=\"",
					 this->cboPartCategories->Text,S"\">",
					 this->txtPartName->Text, S"</PartName>",
					 S"<UnitPrice>", this->txtUnitPrice->Text,
					S"</UnitPrice>");
	 nodNewPart->InnerXml = strNewPart;
	 docXML->DocumentElement->AppendChild(nodNewPart);
	 docXML->Save(S"Parts.xml");

	 // Reset the form in case the user wants to add another part
	 this->cboYears->SelectedIndex = -1;
	 this->cboMakes->SelectedIndex = -1;
	 this->cboModels->SelectedIndex = -1;
	 this->cboPartCategories->Text = S"Miscellaneous";
	 this->txtPartName->Text = S"";
	 this->txtUnitPrice->Text = S"";
	 
	 // We will generate a random number for the item
	 // To start, we will use the miliseconds as a seed
	 DateTime tmeNow = DateTime::Now;
	 int ms = tmeNow.Millisecond;

	 // Now we can generate a random number between 100000 and 999999
	 Random *rndNumber = new Random(ms);

	 // Generate three random characters
	 Char firstCharacter  = static_cast<Char>(rndNumber->Next(65, 90));
	 Char secondCharacter = static_cast<Char>(rndNumber->Next(65, 90));
	 Char thirdCharacter  = static_cast<Char>(rndNumber->Next(65, 90));
	 // Generate a random number made of 4 digits
	 int numberPart = rndNumber->Next(1000, 9999);
	 
	 // Exclude the digits 1 and 0 because they create confusion
	 if( firstCharacter == 'I' || firstCharacter == 'O' )
		 firstCharacter = 'A';
	 if( secondCharacter == 'I' || secondCharacter == 'O' )
		 secondCharacter = 'A';
	 if( thirdCharacter == 'I' || thirdCharacter == 'O' )
		 thirdCharacter = 'A';
	 // Generate a random number between 1 and 3
	 int rndCombination = rndNumber->Next(1, 4);
	 String *strPartNumber = 0;

	 // Create a part number using some algorithm
	 if( rndCombination == 1 )
		 strPartNumber = String::Concat(firstCharacter.ToString(),
						secondCharacter.ToString(), 
						numberPart.ToString(),
						thirdCharacter.ToString());
	 else if( rndCombination == 2 )
		 strPartNumber = String::Concat(firstCharacter.ToString(),
						numberPart.ToString(), 
						secondCharacter.ToString(),
						thirdCharacter.ToString());
	 else if( rndCombination == 3 )
		 strPartNumber = String::Concat(numberPart.ToString(),
						firstCharacter.ToString(), 
						secondCharacter.ToString(),
						thirdCharacter.ToString());
	 else
		 strPartNumber = rndNumber->Next(100000, 999999).ToString();

	 // Display the new number in the Part # text box
	 this->txtPartNumber->Text = strPartNumber;
	 this->cboYears->Focus();
}

Execute the application to test it

Add a few parts as follows (let the computer generate part numbers):

Year	Make	Model	Part Category	Part Name	Unit Price
2002	Audi	A4 Quattro 1.8L Turbo	Exhaust	Exhaust Gasket	1.55
2004	Dodge	Neon SE 2.0L L4	Cooling System	Radiator Fan Assembly	125.95
2002	Audi	A4 Quattro 1.8L Turbo	Drivetrain	Axle Differential Bearing - Left	10.25
2000	Ford	Escort 2.0L L4	Ignition	Crankshaft Position Sensor	18.65
2002	Chevrolet	Silverado 2500 5.3L V8	Ignition	Spark Plugs	1.55
2004	Dodge	Neon SE 2.0L L4	Engine	Oil Pump	112.85
2004	Dodge	Neon SE 2.0L L4	Engine	Exhaust Valve	5.85
1986	Acura	Integra LS 1.8L L4	Electrical	Alternator	110.75
1998	Toyota	Corolla 1.8L L4	Cooling System	Radiator	95.95
2002	Dodge	Dakota 3.9L V6	Electrical	Starter Motor	145.95
2004	Honda	Civic EX 1.7L L4	Emission	Oxygen Sensor	90.55
2002	Audi	A4 Quattro 1.8L Turbo	Electrical	Alternator	305.50
2002	Acura	NSX 3.0L V6	Engine	Oil Filter	7.05
1998	Jeep	Wrangler 2.5L L4	Transfer Case	Input Shaft Seal Transfer Case	6.45
1986	Acura	Integra LS 1.8L L4	Fuel/Air	Fuel Cap (Regular)	4.15
2000	Ford	Escort 2.0L L4	Brake System	Right Caliper Assembly Front	32.85
2004	Dodge	Neon SE 2.0L L4	Clutch	Clutch Release Bearing	25.75
1998	BMW	325I 2.5L L6	Steering	Rack and Pinion Bellow Kit	19.25
2001	Acura	Integra GS 1.8L L4	Electrical	Voltage Regulator	215.75
2001	Audi	S4 2.7L V6	Engine	Timing Belt	35.95
2002	Audi	A4 Quattro 1.8L Turbo	Exhaust	Muffler Hanger	3.35
2002	Chevrolet	Silverado 2500 5.3L V8	Cooling System	Radiator w/Air Tube - w/TOC	215.75
2002	Acura	NSX 3.0L V6	Engine	Oil Drain Plug	1.35
2002	Dodge	Dakota 3.9L V6	Electrical	Circuit Breaker	3.25
2004	Dodge	Neon SE 2.0L L4	Brake System	Brake Pad	20.55
2004	Honda	Civic EX 1.7L L4	Electrical	Fusible Link	3.35
2002	Dodge	Dakota 3.9L V6	Electrical	Circuit Breaker	3.45
2004	Honda	Civic EX 1.7L L4	Transmission-Manual	Differential Bearing	36.75
1998	Toyota	Corolla 1.8L L4	Cooling System	Thermostat Standard Temperature	9.35
2002	Audi	A4 Quattro 1.8L Turbo	Electrical	Cooling Fan Sensor	8.65
2002	Acura	NSX 3.0L V6	Engine	Oil Pump Seal	12.55
2004	Dodge	Neon SE 2.0L L4	Brake System	Master Cylinder w/o ABS w/2 Wheel	102.95
2002	Acura	NSX 3.0L V6	Engine	Valve Stem Oil Seal	1.75
2002	Dodge	Dakota 3.9L V6	Electrical	Fuse	0.40
1998	Toyota	Corolla 1.8L L4	Cooling System	Regular Thermostat	11.15

Close the forms and return to your programming environment


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