XML File Updating



When creating an application that accesses or manipulates an XML file, you may want the user to be able to add new elements to the file. In this exercise, we will review a simple way of adding a new element at the end of existing ones.

Practical Learning: Adding a New Element to an XML File

  1. Start Visual C++ .NET and create a new Windows Forms Application named VideoCollection1
  2. To create a new XML file, on the main menu, click Project -> Add New Item...
  3. In the Templates section, click XML File (.xml)
  4. In the File Name box, type videos and press Enter
  5. Initialize the file as follows:
    <?xml version="1.0" encoding="utf-8"?>
            <title>Fatal Attraction</title>
            <director>Adrian Lyne</director>
            <length>120 Min</length>
  6. Design the form as follows:
    Control Text Name Other
    Label Video Title:    
    TextBox   txtTitle  
    Label Director:    
    TextBox   txtDirector  
    Label (c) Year:   TextAlign: Right
    TextBox   txtYear  
    Label Length:    
    TextBox   txtLength  
    Label Rating:    
    TextBox   txtRating  
    Button New Record btnNewRecord  
    Button Close btnClose  
  7. Double-click each of the buttons and implement their events as follows:
    private: System::Void btnNewRecord_Click(System::Object *  sender, System::EventArgs *  e)
    		 // We will use a DataSet variable to access the file
    		 DataSet* dsVideos = new DataSet;
    		 // Open the XML file
    		 // We will use a DataTable variable to locate a table from the DataSet
    		 DataTable *dtbVideos = new DataTable;
    		 // Retrieve the first table of the DataSet and put it in our DataTable
    		 dtbVideos = dsVideos->Tables->Item[0];
    		 // We will use a DataRow variable for a record
    		 DataRow __gc *drwVideos;
    		 // Initialize our DataRow with the new record of the table
    		 drwVideos = dtbVideos->NewRow();
    		 // Create an entry in the record for each element of the XML File
    		 drwVideos->Item[S"title"]         = this->txtTitle->Text;
           		 drwVideos->Item[S"director"]   = this->txtDirector->Text;
    		 drwVideos->Item[S"copyright"] = this->txtYear->Text;
    		 drwVideos->Item[S"length"]     = this->txtLength->Text;
    		 drwVideos->Item[S"rating"]     = this->txtRating->Text;
    		 // Add the new record to the DataTable
    		 // Update the XML file
    		 // Empty each control of the form in case the user
    		 // wants to create a new record
    		 this->txtTitle->Text       = S"";
    		 this->txtDirector->Text = S"";
    		 this->txtYear->Text      = S"";
    		 this->txtLength->Text  = S"";
    		 this->txtRating->Text   = S"";
    		 // Give focus to the first control that can be updated
    private: System::Void btnClose_Click(System::Object *  sender, System::EventArgs *  e)
  8. Execute the application. Create a new record

Home Copyright © 2004-2010 FunctionX, Inc.