title: CallMethodAction works in MainWindow, but not in UserControl
body: <ol>
  <li><p>It works, if I place the code in MainWindow.</p></li>
  <li><p>It doesn't work, if I place the code in UserControl and then place UserControl 
  in MainWindow.</p></li>
  </ol>
  
  <p>I suppose the problem is with binding. How to make it work?</p>
  
  <ol>
  <li>The next works:</li>
  </ol>
  
  <p><strong>MainWindow.xaml</strong>:</p>
  
  <pre><code>&lt;Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      xmlns:local="clr-namespace:WpfApplication1"
      xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
      xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
      x:Name="window" x:Class="WpfApplication1.MainWindow"
      mc:Ignorable="d"
      Title="MainWindow" Height="350" Width="525" Background="Black"&gt;
  &lt;i:Interaction.Triggers&gt;
      &lt;i:EventTrigger EventName="MouseDown" SourceName="rectangle"&gt;
          &lt;ei:CallMethodAction TargetObject="{Binding ElementName=userControl2}" MethodName="Ok"/&gt;
      &lt;/i:EventTrigger&gt;
  &lt;/i:Interaction.Triggers&gt;
  &lt;Grid&gt;
      &lt;Rectangle x:Name="rectangle" Width="100" Height="100" Fill="White"&gt;&lt;/Rectangle&gt;
      &lt;local:UserControl2 x:Name="userControl2"&gt;&lt;/local:UserControl2&gt;
  &lt;/Grid&gt;&lt;/Window&gt;
  </code></pre>
  
  <ol start="2">
  <li>The next doesn't work:</li>
  </ol>
  
  <p><strong>MainWindow.xaml</strong>:</p>
  
  <pre><code>&lt;Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      xmlns:local="clr-namespace:WpfApplication1"
      xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
      xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
      x:Name="window" x:Class="WpfApplication1.MainWindow"
      mc:Ignorable="d"
      Title="MainWindow" Height="350" Width="525" Background="Black"&gt;
  &lt;Grid&gt;
      &lt;local:UserControl1&gt;&lt;/local:UserControl1&gt;
  &lt;/Grid&gt;&lt;/Window&gt;
  </code></pre>
  
  <p><strong>UserControl1.xaml</strong>:</p>
  
  <pre><code>&lt;UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
       xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
       xmlns:local="clr-namespace:WpfApplication1"
       xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" 
       xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions" 
       x:Name="userControl" 
       x:Class="WpfApplication1.UserControl1"
       mc:Ignorable="d"&gt;
  &lt;i:Interaction.Triggers&gt;
      &lt;i:EventTrigger EventName="MouseDown" SourceName="rectangle"&gt;
          &lt;ei:CallMethodAction TargetObject="{Binding ElementName=userControl2}" MethodName="Ok"/&gt;
      &lt;/i:EventTrigger&gt;
  &lt;/i:Interaction.Triggers&gt;
  &lt;Grid&gt;
      &lt;Rectangle x:Name="rectangle" Width="100" Height="100" Fill="White"&gt;&lt;/Rectangle&gt;
      &lt;local:UserControl2 x:Name="userControl2"&gt;&lt;/local:UserControl2&gt;
  &lt;/Grid&gt;&lt;/UserControl&gt;
  </code></pre>
  
  <p><strong>UserControl2.xaml.cs</strong>:</p>
  
  <pre><code>public partial class UserControl2 : UserControl
  {
      public UserControl2()
      {
          InitializeComponent();
      }
  
      public void Ok()
      {
          MessageBox.Show("a");
      }
  }
  </code></pre>