title: How can I add minimum date validation check for DatePicker in Xamarin
body: <p>I am having two <code>DatePicker</code> (named fromdate and todate) and a button (named as save).</p>
  
  <p>By default, today's date will be populated in both the <code>DatePicker</code>. And I have added minimum date validation ( the user can select only today's or greater date.</p>
  
  <p>If today's date is 30th May and the user selects 15th June from <code>fromdate</code> and clicked ok. Now the default today date is displayed in <code>todate</code>.
  I want a validation like if the user selects 15th June in <code>fromdate</code> and click ok, then the <code>todate</code> should be populated with <code>fromdate</code>.</p>