title: How to place multiple panels into a tab item?
body: <p>I added a tab control and a tab item into my design and want to place 3 dock panels into this tab item horizontally. But I get an error:</p>
  
  <blockquote>
    <p>The property 'Content' is set more than once.</p>
  </blockquote>
  
  <p>I want a design like below.</p>
  
  <p><strong>TabItem1</strong></p>
  
  <p><em>PersonalInformationArea</em>------<em>LocationInformations</em>------EducationInformations<br>
  Name : TextBox1 ---------------City : TextBox3 ------------School : TextBox5<br>
  Surname : Textbox2------------Country : TextBox4</p>
  
  <p>How can I design this?</p>
  
  <pre><code>&lt;TabControl&gt;
      &lt;TabItem Header="Ana Bilgiler"&gt;
          &lt;DockPanel x:Name="dpMainInformations" LastChildFill="False" Width="230"&gt;
              &lt;StackPanel Orientation="Horizontal" DockPanel.Dock="Top" Margin="5,5,5,5"&gt;
                  &lt;TextBlock Text="Müşteri Bilgileri" FontWeight="Bold" HorizontalAlignment="Stretch" Width="200"&gt;&lt;/TextBlock&gt;
              &lt;/StackPanel&gt;
              &lt;StackPanel x:Name="CustName" Orientation="Horizontal" DockPanel.Dock="Top" Margin="5,5,5,5"&gt;
                  &lt;TextBlock Name="lblCustName"  Text="Müşteri adı" Width="100"/&gt;
                  &lt;TextBox x:Name="txtMusteriAdi" Width="100"  Text="{Binding CustName}"  IsReadOnly="{Binding IsControlsEditable}"/&gt;
                  &lt;Button x:Name="btnSelectCust" Content="Seç" Click="Button_Click_5"  IsEnabled="{Binding IsControlsEditable}"/&gt;
              &lt;/StackPanel&gt;
          &lt;/DockPanel&gt;
          &lt;DockPanel LastChildFill="False" Margin="20,5,12,5"&gt;
              &lt;StackPanel  Orientation="Horizontal" DockPanel.Dock="Top" Margin="0,5,0,5"&gt;
                  &lt;TextBlock Text="Uygunsuzluk Bilgileri" FontWeight="Bold"&gt;&lt;/TextBlock&gt;
              &lt;/StackPanel&gt;
              &lt;StackPanel Orientation="Horizontal" DockPanel.Dock="Top" Margin="0,0,0,5"&gt;
                  &lt;TextBlock Name="lblProblemDesc" Text="Tanımı" Width="60"/&gt;
                  &lt;TextBox MinWidth="150" MaxLength="500" Text="{Binding Definition}" UndoLimit="500" VerticalAlignment="Stretch"  TextWrapping="Wrap" AcceptsReturn="True" MinLines="4" MaxWidth="200" Margin="0,0,0,0"  IsReadOnly="{Binding IsControlsEditable}" Height="40" Width="300"/&gt;
              &lt;/StackPanel&gt;
          &lt;/DockPanel&gt;
      &lt;/TabItem&gt;
      &lt;TabItem Header="Kapanma Bilgileri"&gt;
      &lt;/TabItem&gt;
  &lt;/TabControl&gt;
  </code></pre>