title: How to declare MVVM RelayCommand in viewmodel
body: <p>How to use relay command in set, I use the following way, throws interface bug on set method</p>
  
  <pre><code>     public RelayCommand ChartCommand
      {
  
          set
          {
              ChartCommand = new RelayCommand&lt;string&gt;(e =&gt; ExecuteChartCommand(e));
  
          }
      }
      public void ExecuteChartCommand(string vendor)
      {
  
      }
  </code></pre>