title: TextChanged event does not triggered on null when TextBox.Text is absent
body: <p>Does anyone know why when I remove all text from <code>Textbox1</code> it doesn't consider it as a null value but rather as an empty string?</p>
  
  <pre><code>public partial class Form1 : Form
  {
      public Form1()
      {
          InitializeComponent();
      }
  
      private void textBox1_TextChanged(object sender, EventArgs e)
      {
          if (textBox1.Text == null)
          {
              textBox2.Text = "Null";
          }
          else
          {
              textBox2.Text = "Input Positive";
          }
      }
  }
  </code></pre>