Reflection , Attributue

(1). Declare customerized attrubute class ---Class

// Define the Command Handler Custom Attribute:
[AttributeUsage( AttributeTargets.Class )]
public class CommandHandlerAttribute : Attribute
{
  public CommandHandlerAttribute( )
  {
  }
}
(2).--Property

[AttributeUsage( AttributeTargets.Property ) ]
public class DynamicMenuAttribute : System.Attribute
{
  private string _menuText;
  private string _parentText;

  public DynamicMenuAttribute( string CommandText,
    string ParentText )
  {
    _menuText = CommandText;
    _parentText = ParentText;
  }

  public string MenuText
  {
    get { return _menuText; }
    set { _menuText = value; }
  }

  public string ParentText
  {
    get { return _parentText; }
    set { _parentText = value; }
  }
}

(3). Apply for the attributes:

 

[ CommandHandler ]
public class CmdHandler
{
 

[DynamicMenu( "Test Command", "Parent Menu" )]
public EventHandler CmdFunc
{
  get
  {
    if ( theCmdHandler == null )
      theCmdHandler = new System.EventHandler
        (this.DynamicCommandHandler);
    return theCmdHandler;
  }
}

private void DynamicCommandHandler(
  object sender, EventArgs args )
{
  // Contents elided.
}

}

 

(4) Test

// Find all the assemblies in the Add-ins directory:
string AddInsDir = string.Format( "{0}/Addins", Application.StartupPath);
string[] assemblies = Directory.GetFiles( AddInsDir, "*.dll" );
foreach ( string assemblyFile in assemblies )
{
  Assembly asm = Assembly.LoadFrom( assemblyFile );
  // Find and install command handlers from the assembly.
  foreach( System.Type t in asm.GetExportedTypes( ))
  {
   

 if (t.GetCustomAttributes(
    typeof( CommandHandlerAttribute ), false).Length > 0 )
  {
    // Found a command handler type:
    ConstructorInfo ci =
      t.GetConstructor( new Type[0] );
    if ( ci == null ) // No default ctor
      continue;
    object obj = ci.Invoke( null );
    PropertyInfo [] pi = t.GetProperties( );

    // Find the properties that are command
    // handlers
    foreach( PropertyInfo p in pi )
    {
      string menuTxt = "";
      string parentTxt = "";
      object [] attrs = p.GetCustomAttributes(
        typeof ( DynamicMenuAttribute ), false );
      foreach ( Attribute at in attrs )
      {
        DynamicMenuAttribute dym = at as 
          DynamicMenuAttribute;
        if ( dym != null )
        {
          // This is a command handler.
          menuTxt = dym.MenuText;
          parentTxt = dym.ParentText;
          MethodInfo mi = p.GetGetMethod();
          EventHandler h = mi.Invoke( obj, null )
            as EventHandler;
          UpdateMenu( parentTxt, menuTxt, h );
        }
      }
    }
  }
}

private void UpdateMenu( string parentTxt, string txt,
  EventHandler cmdHandler )
{
  MenuItem menuItemDynamic = new MenuItem();
  menuItemDynamic.Index = 0;
  menuItemDynamic.Text = txt;
  menuItemDynamic.Click += cmdHandler;

  //Find the parent menu item.
  foreach ( MenuItem parent in mainMenu.MenuItems )
  {
    if ( parent.Text == parentTxt )
    {
      parent.MenuItems.Add( menuItemDynamic );
      return;
    }
  }
  // Existing parent not found:
  MenuItem newDropDown = new MenuItem();
  newDropDown.Text = parentTxt;
  mainMenu.MenuItems.Add( newDropDown );
  newDropDown.MenuItems.Add( menuItemDynamic );
}