title: Update textbox from a different class
body: <p>I'm relatively new to C# and come a bit stuck.</p>
  
  <p>I've got a Rich Textbox on a form, and I would like to update this from a different class to the Form itself.</p>
  
  <p>I first tried </p>
  
  <pre><code>Form1.outputTextbox.AppendText(string);  
  </code></pre>
  
  <p>but the text box was not accessible, made sense. So instead I tried to make a function. On Form1 I created the function</p>
  
  <pre><code>public void updateTextBox(string new_text)
      {
          outputTextBox.AppendText(new_text);
      }
  </code></pre>
  
  <p>and in the class I used.</p>
  
  <pre><code>Form1.updateTextBox("apple");
  </code></pre>
  
  <p>The problem I'm having is the only way my class can see the function is if I make it the function static, but when I do that get an error "An object reference is required for the nonstatic field, method, or property 'member'"</p>
  
  <p>Am I close or going to wrong way about this completely? Any help would be appricated.</p>