title: Operator "|" cannot be applied to operands of type 'string' and 'string'
body: <p>Hello everyone so I'm having the problem that its on the title ( Operator <code>"|"</code> cannot be applied to operands of type <code>string</code> and <code>string</code>)</p>
  
  <p>Here is the code that I'm running at the moment</p>
  
  <pre><code>if ( (tb_id.Text="") | (tbnome.Text = "") | (tbpreco.Text = "") | (tbquant.Text = "") )
  {
          MessageBox.Show("Erro, Voce não inseriu algo"); 
  }
  </code></pre>
  
  <p>I really don't know why its happening, I already searched around stackoverflow and other websites and forums but still couldn't see the error.</p>