title: How to validate input text length in material input?
body: <p>I am developing an application using angular dart. I am using angular dart material input for getting input from user. </p>
  
  <p>I have a multiline text input for which I use material input and type="text".</p>
  
  <p>I have made this field "required" but the problem is when the user enters white space or enter, the "required" is gone. I need a attribute where i can specify a constraint that at least one non-white space character must be entered.</p>
  
  <p>How to achieve this?</p>
  
  <p>Here is my code where I have used material input:</p>
  
  <pre><code>&lt;material-input
      ngControl="textAnswer" [(ngModel)]="answer" multiline
      type="text" label="Your answer" required&gt;
  &lt;/material-input&gt;
  </code></pre>