XML File Updating

Introduction

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"?> <videos> <video> <title>Fatal Attraction</title> <director>Adrian Lyne</director> <copyright>1987</copyright> <length>120 Min</length> <rating>R</rating> </video> </videos>

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 dsVideos->ReadXml(S"videos.xml"); // 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 dtbVideos->Rows->Add(drwVideos); // Update the XML file dsVideos->WriteXml(S"videos.xml"); // 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 this->txtTitle->Focus(); } private: System::Void btnClose_Click(System::Object * sender, System::EventArgs * e) { Close(); }

8. Execute the application. Create a new record