Adding a New Element With Attributes



One of the jobs performed when managing the nodes of an XML file consists of adding a new element with its accompanying attribute(s) to the list.

To add a new element with its attribute(s), you should open it using the XmlDocument class to start. To actually add element, you can use an XmlElement variable. The XmlDocument class is equipped with the CreateElement() method that allows you to add a new element. The XmlDocument::CreateElement() method returns an XmlElement value that you can assign to your declared XmlElement. Once you have created the new node, to add one or more attributes to it, you can call the XmlElement::SetAttribute() method.


Practical Learning: Adding a New Element With Attributes

  1. Start Microsoft Visual C++ .Net and create a new Windows Forms Application named CarInventory2
  2. Create a new XML file named Cars
  3. Complete it the following elements:
    <?xml version="1.0" encoding="utf-8"?>
    	<car Make="Ford" Model="Taurus" />
    	<car Make="Mazda" Model="626" />
  4. Add a DataGrid control to the form
  5. Add a Button control to the form. Change its Text to Load and its Name to btnLoad
  6. Add another Button to the form. Change its Text to Close and its Name to btnClose
  7. Double-click an unoccupied area on the form
  8. Return to the form and double-click the Load and the Close buttons
  9. Implement the events as follows:
    #pragma once
    namespace CarInventory2
    	using namespace System;
    	using namespace System::ComponentModel;
    	using namespace System::Collections;
    	using namespace System::Windows::Forms;
    	using namespace System::Data;
    	using namespace System::Drawing;
    	using namespace System::Xml;
    	/// <summary> 
    	/// Summary for Form1
    	/// WARNING: If you change the name of this class, you will need to change the 
    	///          'Resource File Name' property for the managed resource compiler tool 
    	///          associated with all .resx files this class depends on.  Otherwise,
    	///          the designers will not be able to interact properly with localized
    	///          resources associated with this form.
    	/// </summary>
    	public __gc class Form1 : public System::Windows::Forms::Form
    		void Dispose(Boolean disposing)
    			if (disposing && components)
    	private: System::Windows::Forms::DataGrid *  dataGrid1;
    	private: System::Windows::Forms::Button *  btnLoad;
    	private: System::Windows::Forms::Button *  btnClose;
    	private: System::Windows::Forms::GroupBox *  groupBox1;
    	private: System::Windows::Forms::Label *  label1;
    	private: System::Windows::Forms::TextBox *  txtMake;
    	private: System::Windows::Forms::Label *  label2;
    	private: System::Windows::Forms::TextBox *  txtModel;
    	private: System::Windows::Forms::Button *  btnAdd;
    		/// <summary>
    		/// Required designer variable.
    		/// </summary>
    		System::ComponentModel::Container * components;
    		DataSet *dsCarInfo;
    		/// <summary>
    		/// Required method for Designer support - do not modify
    		/// the contents of this method with the code editor.
    		/// </summary>
    		void InitializeComponent(void)
    			. . . 
    	private: System::Void btnLoad_Click(System::Object *  sender, System::EventArgs *  e)
    				 this->dataGrid1->DataSource = dsCarInfo;
    				 this->dataGrid1->DataMember = S"car";
    	private: System::Void btnClose_Click(System::Object *  sender, System::EventArgs *  e)
    private: System::Void Form1_Load(System::Object *  sender, System::EventArgs *  e)
    			 dsCarInfo = new DataSet(S"CarsInformation");
  10. Test the application:
  11. Close it and return to MSVC
  12. To prepare for new items, change the design of the form as follows:
  13. Change the names of the new text boxes to txtMake and txtModel
  14. Change the name of the new button to btnAdd and double-click it
  15. Implement its event as follows:
    private: System::Void btnAdd_Click(System::Object *  sender, System::EventArgs *  e)
    		 // Retrieve the name of the make and the name of the model
    		 String *strMake  = this->txtMake->Text;
    		 String *strModel = this->txtModel->Text;
    		 // Check that there is a make car to add
    		 if( strMake->Equals(S"") )
    			 MessageBox::Show(S"No car make to add");
    		 // Check that there is a model car to add
    		 if( strModel->Equals(S"") )
    			 MessageBox::Show(S"No car model to add");
    		 // Declare an XmlDocument that will be used to add a new item
    		 XmlDocument* XmlDoc = new XmlDocument();
    		 try {
    			 // Remove any item from the data set
    			 // Get the XML file and load it in the XmlDocument variable
    			 // Create the new element
    			 XmlElement *Elm = XmlDoc->CreateElement(S"car");
    			 // Create its attributes
    			 Elm->SetAttribute(S"Make", strMake);
    			 Elm->SetAttribute(S"Model", strModel);
    			 // Add the new element to the file...
    			 // ... and save the document
    			 // Reload the XML file in the data set
    			 // Display the new changes in the data grid
    			 this->dataGrid1->DataSource = dsCarInfo;
    			 this->dataGrid1->DataMember = S"car";
    			 // Since the new items have just been added,
    			 // we can empty the text boxes
    			 this->txtMake->Text = S"";
    			 this->txtModel->Text = S"";
    		 catch (Exception *e)
  16. Execute the application to test it. Then click the Load button first and test adding a new item

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