text: I want to create a class library (dll file) of the WPF TextBox with extended functionality. But i want to change one part of the TextBox's default style (IsMouseOver property trigger).
  I created a new WPF user control library project, deleted the generated .XAML and .cs files from it, and added a new class file. Then i derived from the TextBox class, but i don't know how to access the style XAML.
  I can't figure out how this supposed to be done..
  Inside my project i currently have only this .cs file, and no .XAML file:
  namespace CustomControls
  {
  public class CustomTextBox : TextBox
  {
  private string customProperty;
  public string CustomProperty
  {
  get { return customProperty; }
  set { customProperty = value; }
  }
  }
  }
  You can do something like this
  <TextBox x: </TextBox>
  Code behind
  public partial class CustomTextBox : TextBox { public CustomTextBox() { InitializeComponent(); } }
  Now you can do whatever you want to do in your xaml (edit template, apply style etc), and you'll have access to it from code behind.