diff --git a/DarkUI/DarkUI.csproj b/DarkUI/DarkUI.csproj
index 3156143..f02f8c3 100644
--- a/DarkUI/DarkUI.csproj
+++ b/DarkUI/DarkUI.csproj
@@ -106,6 +106,7 @@
     <Compile Include="Docking\DarkToolWindow.cs">
       <SubType>UserControl</SubType>
     </Compile>
+    <Compile Include="Docking\EventArgs\DockContentEventArgs.cs" />
     <Compile Include="Docking\Items\DarkDockSplitter.cs" />
     <Compile Include="Docking\Items\DarkDockTab.cs" />
     <Compile Include="Docking\Items\DarkDockTabArea.cs" />
diff --git a/DarkUI/Docking/DarkDockGroup.cs b/DarkUI/Docking/DarkDockGroup.cs
index 17dcca4..22235ea 100644
--- a/DarkUI/Docking/DarkDockGroup.cs
+++ b/DarkUI/Docking/DarkDockGroup.cs
@@ -52,6 +52,8 @@ namespace DarkUI.Docking
             Order = order;
 
             _tabArea = new DarkDockTabArea(DockArea);
+
+            DockPanel.ActiveContentChanged += DockPanel_ActiveContentChanged;
         }
 
         #endregion
@@ -282,6 +284,10 @@ namespace DarkUI.Docking
 
             var width = ClientRectangle.Width - Padding.Horizontal - _tabArea.DropdownRectangle.Width;
             var offsetArea = new Rectangle(Padding.Left, 0, width, 0);
+
+            if (!_tabs.ContainsKey(DockPanel.ActiveContent))
+                return;
+
             var tab = _tabs[DockPanel.ActiveContent];
 
             if (tab.ClientRectangle.IsEmpty)
@@ -438,6 +444,23 @@ namespace DarkUI.Docking
             DockPanel.ActiveContent = content;
         }
 
+        private void DockPanel_ActiveContentChanged(object sender, DockContentEventArgs e)
+        {
+            if (!_contents.Contains(e.Content))
+                return;
+
+            if (e.Content == VisibleContent)
+                return;
+
+            VisibleContent = e.Content;
+
+            foreach (var content in _contents)
+                content.Visible = content == VisibleContent;
+
+            EnsureVisible();
+            Invalidate();
+        }
+
         #endregion
 
         #region Render Region
diff --git a/DarkUI/Docking/DarkDockPanel.cs b/DarkUI/Docking/DarkDockPanel.cs
index bd87fc1..f2b6744 100644
--- a/DarkUI/Docking/DarkDockPanel.cs
+++ b/DarkUI/Docking/DarkDockPanel.cs
@@ -1,5 +1,6 @@
 using DarkUI.Config;
 using DarkUI.Win32;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Windows.Forms;
@@ -8,12 +9,19 @@ namespace DarkUI.Docking
 {
     public class DarkDockPanel : UserControl
     {
+        #region Event Region
+
+        public event EventHandler<DockContentEventArgs> ActiveContentChanged;
+
+        #endregion
+
         #region Field Region
 
         private List<DarkDockContent> _contents;
         private Dictionary<DarkDockArea, DarkDockRegion> _regions;
 
         private DarkDockContent _activeContent;
+        private bool _switchingContent = false;
 
         #endregion
 
@@ -24,6 +32,11 @@ namespace DarkUI.Docking
             get { return _activeContent; }
             internal set
             {
+                if (_switchingContent)
+                    return;
+
+                _switchingContent = true;
+
                 _activeContent = value;
 
                 ActiveGroup = _activeContent.DockGroup;
@@ -31,6 +44,11 @@ namespace DarkUI.Docking
 
                 foreach (var region in _regions.Values)
                     region.Redraw();
+
+                if (ActiveContentChanged != null)
+                    ActiveContentChanged(this, new DockContentEventArgs(_activeContent));
+
+                _switchingContent = false;
             }
         }
 
diff --git a/DarkUI/Docking/EventArgs/DockContentEventArgs.cs b/DarkUI/Docking/EventArgs/DockContentEventArgs.cs
new file mode 100644
index 0000000..13ae74d
--- /dev/null
+++ b/DarkUI/Docking/EventArgs/DockContentEventArgs.cs
@@ -0,0 +1,14 @@
+using System;
+
+namespace DarkUI.Docking
+{
+    public class DockContentEventArgs : EventArgs
+    {
+        public DarkDockContent Content { get; private set; }
+
+        public DockContentEventArgs(DarkDockContent content)
+        {
+            Content = content;
+        }
+    }
+}