Question

I have a textbox, when its content changed, I want to query the xml file for elements that match the text in the textbox and display the result in a listbox.

My current code is:

  private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
    {
        var xElem = XElement.Load("ProductTable.xml");
        ...

How should I code so that Load is called only once? As is, each time a keystroke is entered, the xml file is (re)loaded. Thanks.

Answer 1

Move xElem to be your class’s field. Then in TextChanged handler check for null:

class MyControl : UserControl
{
   XDocument productTableDocument;

   private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
   {
      if (productTableDocument == null)   
      {
         productTableDocument = XDocument.Load("ProductTable.xml");
      }
      // continue working with not null productTableDocument
   }
}