using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Markup;
using System.Windows;
using System.Windows.Input;

namespace AttachedCommandBehavior
{
    /// <summary>
    /// Defines the attached properties to create a CommandBehaviorBinding
    /// </summary>
    public class CommandBehavior
    {
        #region Behavior

        /// <summary>
        /// Behavior Attached Dependency Property
        /// </summary>
        private static readonly DependencyProperty BehaviorProperty =
            DependencyProperty.RegisterAttached("Behavior", typeof(CommandBehaviorBinding), typeof(CommandBehavior),
                new FrameworkPropertyMetadata((CommandBehaviorBinding)null));

        /// <summary>
        /// Gets the Behavior property. 
        /// </summary>
        private static CommandBehaviorBinding GetBehavior(DependencyObject d)
        {
            return (CommandBehaviorBinding)d.GetValue(BehaviorProperty);
        }

        /// <summary>
        /// Sets the Behavior property.  
        /// </summary>
        private static void SetBehavior(DependencyObject d, CommandBehaviorBinding value)
        {
            d.SetValue(BehaviorProperty, value);
        }

        #endregion

        #region Command

        /// <summary>
        /// Command Attached Dependency Property
        /// </summary>
        public static readonly DependencyProperty CommandProperty =
            DependencyProperty.RegisterAttached("Command", typeof(ICommand), typeof(CommandBehavior),
                new FrameworkPropertyMetadata((ICommand)null,
                    new PropertyChangedCallback(OnCommandChanged)));

        /// <summary>
        /// Gets the Command property.  
        /// </summary>
        public static ICommand GetCommand(DependencyObject d)
        {
            return (ICommand)d.GetValue(CommandProperty);
        }

        /// <summary>
        /// Sets the Command property. 
        /// </summary>
        public static void SetCommand(DependencyObject d, ICommand value)
        {
            d.SetValue(CommandProperty, value);
        }

        /// <summary>
        /// Handles changes to the Command property.
        /// </summary>
        private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            CommandBehaviorBinding binding = FetchOrCreateBinding(d);
            binding.Command = (ICommand)e.NewValue;
        }

        #endregion

        #region CommandParameter

        /// <summary>
        /// CommandParameter Attached Dependency Property
        /// </summary>
        public static readonly DependencyProperty CommandParameterProperty =
            DependencyProperty.RegisterAttached("CommandParameter", typeof(object), typeof(CommandBehavior),
                new FrameworkPropertyMetadata((object)null,
                    new PropertyChangedCallback(OnCommandParameterChanged)));

        /// <summary>
        /// Gets the CommandParameter property.  
        /// </summary>
        public static object GetCommandParameter(DependencyObject d)
        {
            return (object)d.GetValue(CommandParameterProperty);
        }

        /// <summary>
        /// Sets the CommandParameter property. 
        /// </summary>
        public static void SetCommandParameter(DependencyObject d, object value)
        {
            d.SetValue(CommandParameterProperty, value);
        }

        /// <summary>
        /// Handles changes to the CommandParameter property.
        /// </summary>
        private static void OnCommandParameterChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            CommandBehaviorBinding binding = FetchOrCreateBinding(d);
            binding.CommandParameter = e.NewValue;
        }

        #endregion

        #region Event

        /// <summary>
        /// Event Attached Dependency Property
        /// </summary>
        public static readonly DependencyProperty EventProperty =
            DependencyProperty.RegisterAttached("Event", typeof(string), typeof(CommandBehavior),
                new FrameworkPropertyMetadata((string)String.Empty,
                    new PropertyChangedCallback(OnEventChanged)));

        /// <summary>
        /// Gets the Event property.  This dependency property 
        /// indicates ....
        /// </summary>
        public static string GetEvent(DependencyObject d)
        {
            return (string)d.GetValue(EventProperty);
        }

        /// <summary>
        /// Sets the Event property.  This dependency property 
        /// indicates ....
        /// </summary>
        public static void SetEvent(DependencyObject d, string value)
        {
            d.SetValue(EventProperty, value);
        }

        /// <summary>
        /// Handles changes to the Event property.
        /// </summary>
        private static void OnEventChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            CommandBehaviorBinding binding = FetchOrCreateBinding(d);
            //check if the Event is set. If yes we need to rebind the Command to the new event and unregister the old one
            if (binding.Event != null && binding.Owner != null)
                binding.Dispose();
            //bind the new event to the command
            binding.BindEvent(d, e.NewValue.ToString());
        }

        #endregion

        #region Helpers
        //tries to get a CommandBehaviorBinding from the element. Creates a new instance if there is not one attached
        private static CommandBehaviorBinding FetchOrCreateBinding(DependencyObject d)
        {
            CommandBehaviorBinding binding = CommandBehavior.GetBehavior(d);
            if (binding == null)
            {
                binding = new CommandBehaviorBinding();
                CommandBehavior.SetBehavior(d, binding);
            }
            return binding;
        }
        #endregion

    }

}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using System.Reflection;
using System.Windows;

namespace AttachedCommandBehavior
{
    /// <summary>
    /// Defines the command behavior binding
    /// </summary>
    public class CommandBehaviorBinding : IDisposable
    {
        #region Properties
        /// <summary>
        /// Get the owner of the CommandBinding ex: a Button
        /// This property can only be set from the BindEvent Method
        /// </summary>
        public DependencyObject Owner { get; private set; }
        /// <summary>
        /// The command to execute when the specified event is raised
        /// </summary>
        public ICommand Command { get; set; }
        /// <summary>
        /// Gets or sets a CommandParameter
        /// </summary>
        public object CommandParameter { get; set; }
        /// <summary>
        /// The event name to hook up to
        /// This property can only be set from the BindEvent Method
        /// </summary>
        public string EventName { get; private set; }
        /// <summary>
        /// The event info of the event
        /// </summary>
        public EventInfo Event { get; private set; }
        /// <summary>
        /// Gets the EventHandler for the binding with the event
        /// </summary>
        public Delegate EventHandler { get; private set; }

        #endregion

        //Creates an EventHandler on runtime and registers that handler to the Event specified
        public void BindEvent(DependencyObject owner, string eventName)
        {
            EventName = eventName;
            Owner = owner;
            Event = Owner.GetType().GetEvent(EventName, BindingFlags.Public | BindingFlags.Instance);
            if (Event == null)
                throw new InvalidOperationException(String.Format("Could not resolve event name {0}", EventName));

            //Create an event handler for the event that will call the ExecuteCommand method
            EventHandler = EventHandlerGenerator.CreateDelegate(
                Event.EventHandlerType, typeof(CommandBehaviorBinding).GetMethod("ExecuteCommand", BindingFlags.Public | BindingFlags.Instance), this);
            //Register the handler to the Event
            Event.AddEventHandler(Owner, EventHandler);
        }

        /// <summary>
        /// Executes the command
        /// </summary>
        public void ExecuteCommand()
        {
            if (Command.CanExecute(CommandParameter))
                Command.Execute(CommandParameter);
        }

        #region IDisposable Members
        bool disposed = false;
        /// <summary>
        /// Unregisters the EventHandler from the Event
        /// </summary>
        public void Dispose()
        {
            if (!disposed)
            {
                Event.RemoveEventHandler(Owner, EventHandler);
                disposed = true;
            }
        }

        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection.Emit;
using System.Reflection;

namespace AttachedCommandBehavior
{
    /// <summary>
    /// Generates delegates according to the specified signature on runtime
    /// </summary>
    public static class EventHandlerGenerator
    {
        /// <summary>
        /// Generates a delegate with a matching signature of the supplied eventHandlerType
        /// This method only supports Events that have a delegate of type void
        /// </summary>
        /// <param name="eventInfo">The delegate type to wrap. Note that this must always be a void delegate</param>
        /// <param name="methodToInvoke">The method to invoke</param>
        /// <param name="methodInvoker">The object where the method resides</param>
        /// <returns>Returns a delegate with the same signature as eventHandlerType that calls the methodToInvoke inside</returns>
        public static Delegate CreateDelegate(Type eventHandlerType, MethodInfo methodToInvoke, object methodInvoker)
        {
            //Get the eventHandlerType signature
            var eventHandlerInfo = eventHandlerType.GetMethod("Invoke");
            Type returnType = eventHandlerInfo.ReturnParameter.ParameterType;
            if (returnType != typeof(void))
                throw new ApplicationException("Delegate has a return type. This only supprts event handlers that are void");

            ParameterInfo[] delegateParameters = eventHandlerInfo.GetParameters();
            //Get the list of type of parameters. Please note that we do + 1 because we have to push the object where the method resides i.e methodInvoker parameter
            Type[] hookupParameters = new Type[delegateParameters.Length + 1];
            hookupParameters[0] = methodInvoker.GetType();
            for (int i = 0; i < delegateParameters.Length; i++)
                hookupParameters[i + 1] = delegateParameters[i].ParameterType;

            DynamicMethod handler = new DynamicMethod("", null,
                hookupParameters, typeof(EventHandlerGenerator));

            ILGenerator eventIL = handler.GetILGenerator();

            //load the parameters or everything will just BAM :)
            LocalBuilder local = eventIL.DeclareLocal(typeof(object[]));
            eventIL.Emit(OpCodes.Ldc_I4, delegateParameters.Length + 1);
            eventIL.Emit(OpCodes.Newarr, typeof(object));
            eventIL.Emit(OpCodes.Stloc, local);

            //start from 1 because the first item is the instance. Load up all the arguments
            for (int i = 1; i < delegateParameters.Length + 1; i++)
            {
                eventIL.Emit(OpCodes.Ldloc, local);
                eventIL.Emit(OpCodes.Ldc_I4, i);
                eventIL.Emit(OpCodes.Ldarg, i);
                eventIL.Emit(OpCodes.Stelem_Ref);
            }

            eventIL.Emit(OpCodes.Ldloc, local);

            //Load as first argument the instance of the object for the methodToInvoke i.e methodInvoker
            eventIL.Emit(OpCodes.Ldarg_0);

            //Now that we have it all set up call the actual method that we want to call for the binding
            eventIL.EmitCall(OpCodes.Call, methodToInvoke, null);

            eventIL.Emit(OpCodes.Pop);
            eventIL.Emit(OpCodes.Ret);

            //create a delegate from the dynamic method
            return handler.CreateDelegate(eventHandlerType, methodInvoker);
        }

    }
}

<Border Background="Aqua" 
local:CommandBehavior.Event="MouseDown" 
local:CommandBehavior.Command="{Binding SomeCommand}"
local:CommandBehavior.CommandParameter="{Binding}"/>