title: Update slider value in MVVM
body: <p>Originally I have a button event in code behind.</p>
  
  <pre><code>private async void SomeCommand(object sender, RoutedEventArgs e)
  {
      MySlider.Value = MySlider.Value - 1;
  </code></pre>
  
  <p>In my XAML.</p>
  
  <pre><code> &lt;Button Command="{Binding SomeCommand}"&gt;Do Something&lt;/Button&gt;
  </code></pre>
  
  <p>Now I am going to use MVVM.</p>
  
  <pre><code>public class MyViewModel : ViewModel
  {
      private readonly ICommand someCommand;
      public MyViewModel()
      {
          this.someCommand = new DelegateCommand(this.DoSomething, this.CanDoSomething);
      }
  
      public ICommand SomeCommand
      {
          get { return this.someCommand; }
      }
  
      private void DoSomething(object state)
      {
          // do something here
      }
  
      private bool CanDoSomething(object state)
      {
         // return true/false here is enabled/disable button
      }
  }
  </code></pre>
  
  <p>I don't know what is the code for it inside the method <code>DoSomething</code>?</p>