This is a very useful delegate command for WPF. Note I did not write this and cant locate where I found the original source.

DelegateCommand.cs

using System;
using System.Collections.Generic;
using System.Windows.Input;

namespace DelegateCommands
{
    /// <summary>
    ///     This class allows delegating the commanding logic to methods passed as parameters,
    ///     and enables a View to bind commands to objects that are not part of the element tree.
    /// </summary>
    public class DelegateCommand : ICommand
    {
        #region cTor
        /// <summary>
        /// private constructor
        /// </summary>
        private DelegateCommand()
        {

        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        public DelegateCommand(Action executeMethod)
            : this(executeMethod, null, false)
        {
        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed with a call back method to enable \ disable the execution
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        /// <param name="canExecuteMethod">the function to execute to determine if the command can be run</param>
        public DelegateCommand(Action executeMethod, Func<bool> canExecuteMethod)
            : this(executeMethod, canExecuteMethod, false)
        {
        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed with a call back method to enable \ disable the execution. Set the Automatic Requery Flag to disable command requery
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        /// <param name="canExecuteMethod">the function to execute to determine if the command can be run</param>
        /// <param name="isAutomaticRequeryDisabled">flag to set the automatic requery method</param>
        public DelegateCommand(Action executeMethod, Func<bool> canExecuteMethod, bool isAutomaticRequeryDisabled)
        {
            if (executeMethod == null)
                throw new ArgumentNullException("executeMethod");
            _executeMethod = executeMethod;
            _canExecuteMethod = canExecuteMethod;
            _isAutomaticRequeryDisabled = isAutomaticRequeryDisabled;
        }

        #endregion

        #region Methods

        /// <summary>
        ///     Method to determine if the command can be executed
        /// </summary>
        public bool CanExecute()
        {
            if (_canExecuteMethod != null)
            {
                return _canExecuteMethod();
            }
            return true;
        }

        /// <summary>
        ///     The commands routed event handler
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        public void CanExecuteRoutedEventHandler(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = this.CanExecute();
        }


        /// <summary>
        ///     Execution of the command
        /// </summary>
        public void Execute()
        {
            if (_executeMethod != null)
            {
                _executeMethod();
            }
        }

        public void ExecutedRoutedEventHandler(object sender, ExecutedRoutedEventArgs e)
        {
            this.Execute();
        }

        /// <summary>
        ///     Property to enable or disable CommandManager's automatic requery on this command
        /// </summary>
        public bool IsAutomaticRequeryDisabled
        {
            get
            {
                return _isAutomaticRequeryDisabled;
            }
            set
            {
                if (_isAutomaticRequeryDisabled != value)
                {
                    if (value)
                    {
                        CommandManagerHelper.RemoveHandlersFromRequerySuggested(_canExecuteChangedHandlers);
                    }
                    else
                    {
                        CommandManagerHelper.AddHandlersToRequerySuggested(_canExecuteChangedHandlers);
                    }
                    _isAutomaticRequeryDisabled = value;
                }
            }
        }

        /// <summary>
        ///     Raises the CanExecuteChaged event
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            OnCanExecuteChanged();
        }

        /// <summary>
        ///     Protected virtual method to raise CanExecuteChanged event
        /// </summary>
        protected virtual void OnCanExecuteChanged()
        {
            CommandManagerHelper.CallWeakReferenceHandlers(_canExecuteChangedHandlers);
        }

        #endregion

        #region ICommand Members

        /// <summary>
        ///     ICommand.CanExecuteChanged implementation
        /// </summary>
        public event EventHandler CanExecuteChanged
        {
            add
            {
                if (!_isAutomaticRequeryDisabled)
                {
                    CommandManager.RequerySuggested += value;
                }
                CommandManagerHelper.AddWeakReferenceHandler(ref _canExecuteChangedHandlers, value, 2);
            }
            remove
            {
                if (!_isAutomaticRequeryDisabled)
                {
                    CommandManager.RequerySuggested -= value;
                }
                CommandManagerHelper.RemoveWeakReferenceHandler(_canExecuteChangedHandlers, value);
            }
        }

        /// <summary>
        /// ICommand.CanExecute implementation
        /// </summary>
        /// <param name="parameter">the object parameter</param>
        /// <returns></returns>
        bool ICommand.CanExecute(object parameter)
        {
            return CanExecute();
        }

        /// <summary>
        /// ICommand.Execute implenetation
        /// </summary>
        /// <param name="parameter">the command parameter</param>
        void ICommand.Execute(object parameter)
        {
            Execute();
        }

        #endregion

        #region Fields

        /// <summary>
        /// the _execution method
        /// </summary>
        private readonly Action _executeMethod = null;

        /// <summary>
        /// the can execute function
        /// </summary>
        private readonly Func<bool> _canExecuteMethod = null;

        /// <summary>
        /// automatic requery disabled flag
        /// </summary>
        private bool _isAutomaticRequeryDisabled = false;

        /// <summary>
        /// can execute changed handlers
        /// </summary>
        private List<WeakReference> _canExecuteChangedHandlers;

        #endregion



    }


    /// <summary>
    ///     This class allows delegating the commanding logic to methods passed as parameters,
    ///     and enables a View to bind commands to objects that are not part of the element tree.
    /// </summary>
    /// <typeparam name="T">Type of the parameter passed to the delegates</typeparam>
    public class DelegateCommand<T> : ICommand
    {
        #region Constructors

        /// <summary>
        /// private constructor
        /// </summary>
        private DelegateCommand()
        {
            throw new Exception("private constructor");
        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        public DelegateCommand(Action<T> executeMethod)
            : this(executeMethod, null, false)
        {
        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed with a call back method to enable \ disable the execution
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        /// <param name="canExecuteMethod">the function to execute to determine if the command can be run</param>
        public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
            : this(executeMethod, canExecuteMethod, false)
        {
        }

        /// <summary>
        /// Creates a new delegate command by passing in the execute method when the command is executed with a call back method to enable \ disable the execution. Set the Automatic Requery Flag to disable command requery
        /// </summary>
        /// <param name="executeMethod">the execute method</param>
        /// <param name="canExecuteMethod">the function to execute to determine if the command can be run</param>
        /// <param name="isAutomaticRequeryDisabled">flag to set the automatic requery method</param>
        public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod, bool isAutomaticRequeryDisabled)
        {
            if (executeMethod == null)
            {
                throw new ArgumentNullException("executeMethod");
            }

            _executeMethod = executeMethod;
            _canExecuteMethod = canExecuteMethod;
            _isAutomaticRequeryDisabled = isAutomaticRequeryDisabled;
        }

        #endregion

        #region Methods

        /// <summary>
        ///     Method to determine if the command can be executed
        /// </summary>
        /// <param name="parameter">the object parameter (optional)</param>
        public bool CanExecute(T parameter)
        {
            if (_canExecuteMethod != null)
                return _canExecuteMethod(parameter);
            return true;
        }

        /// <summary>
        ///     Execution of the command
        /// </summary>
        /// <param name="parameter">the object parameter (optional)</param>
        public void Execute(T parameter)
        {
            if (_executeMethod != null)
                _executeMethod(parameter);
        }

        /// <summary>
        ///     Raises the CanExecuteChaged event
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            OnCanExecuteChanged();
        }

        /// <summary>
        ///     Protected virtual method to raise CanExecuteChanged event
        /// </summary>
        protected virtual void OnCanExecuteChanged()
        {
            CommandManagerHelper.CallWeakReferenceHandlers(_canExecuteChangedHandlers);
        }
        #endregion

        #region Properties

        /// <summary>
        ///     Property to enable or disable CommandManager's automatic requery on this command
        /// </summary>
        public bool IsAutomaticRequeryDisabled
        {
            get
            {
                return _isAutomaticRequeryDisabled;
            }
            set
            {
                if (_isAutomaticRequeryDisabled != value)
                {
                    if (value)
                        CommandManagerHelper.RemoveHandlersFromRequerySuggested(_canExecuteChangedHandlers);
                    else
                        CommandManagerHelper.AddHandlersToRequerySuggested(_canExecuteChangedHandlers);
                    _isAutomaticRequeryDisabled = value;
                }
            }
        }

        #endregion

        #region ICommand Members

        /// <summary>
        ///     ICommand.CanExecuteChanged implementation
        /// </summary>
        public event EventHandler CanExecuteChanged
        {
            add
            {
                if (!_isAutomaticRequeryDisabled)
                {
                    CommandManager.RequerySuggested += value;
                }
                CommandManagerHelper.AddWeakReferenceHandler(ref _canExecuteChangedHandlers, value, 2);
            }
            remove
            {
                if (!_isAutomaticRequeryDisabled)
                {
                    CommandManager.RequerySuggested -= value;
                }
                CommandManagerHelper.RemoveWeakReferenceHandler(_canExecuteChangedHandlers, value);
            }
        }

        /// <summary>
        /// ICommand.CanExecute
        /// </summary>
        /// <param name="parameter">the object paramter</param>
        /// <returns></returns>
        bool ICommand.CanExecute(object parameter)
        {
            if (parameter == null &&
                typeof(T).IsValueType)
                return true;
            return CanExecute((T)parameter);
        }

        /// <summary>
        /// ICommand.Execute method
        /// </summary>
        /// <param name="parameter">the parameter</param>
        void ICommand.Execute(object parameter)
        {
            Execute((T)parameter);
        }

        #endregion

        #region Fields
        /// <summary>
        /// the execute method
        /// </summary>
        private readonly Action<T> _executeMethod = null;

        /// <summary>
        /// the can execute method
        /// </summary>
        private readonly Func<T, bool> _canExecuteMethod = null;

        /// <summary>
        /// flag if automatic requery is disabled
        /// </summary>
        private bool _isAutomaticRequeryDisabled = false;

        /// <summary>
        /// can execute changed handlers
        /// </summary>
        private List<WeakReference> _canExecuteChangedHandlers;

        #endregion
    }


    /// <summary>
    ///     This class contains methods for the CommandManager that help avoid memory leaks by
    ///     using weak references.
    /// </summary>
    internal class CommandManagerHelper
    {
        #region Methods
        /// <summary>
        /// calls the weak reference handlers
        /// </summary>
        /// <param name="handlers">list of handlers</param>
        internal static void CallWeakReferenceHandlers(List<WeakReference> handlers)
        {
            if (handlers != null)
            {
                // Take a snapshot of the handlers before we call out to them since the handlers
                // could cause the array to me modified while we are reading it.

                EventHandler[] callees = new EventHandler[handlers.Count];
                int count = 0;

                for (int i = handlers.Count - 1; i >= 0; i--)
                {
                    WeakReference reference = handlers[i];
                    EventHandler handler = reference.Target as EventHandler;
                    if (handler == null)
                    {
                        // Clean up old handlers that have been collected
                        handlers.RemoveAt(i);
                    }
                    else
                    {
                        callees[count] = handler;
                        count++;
                    }
                }

                // Call the handlers that we snapshotted
                for (int i = 0; i < count; i++)
                {
                    EventHandler handler = callees[i];
                    handler(null, EventArgs.Empty);
                }
            }
        }

        /// <summary>
        /// Adds handlers to the request suggested actions
        /// </summary>
        /// <param name="handlers">a reference of weak handlers</param>
        internal static void AddHandlersToRequerySuggested(List<WeakReference> handlers)
        {
            if (handlers != null)
            {
                foreach (WeakReference handlerRef in handlers)
                {
                    EventHandler handler = handlerRef.Target as EventHandler;
                    if (handler != null)
                    {
                        CommandManager.RequerySuggested += handler;
                    }
                }
            }
        }


        /// <summary>
        /// removes handlers from the request suggested
        /// </summary>
        /// <param name="handlers">the list</param>
        internal static void RemoveHandlersFromRequerySuggested(List<WeakReference> handlers)
        {
            if (handlers != null)
            {
                foreach (WeakReference handlerRef in handlers)
                {
                    EventHandler handler = handlerRef.Target as EventHandler;
                    if (handler != null)
                    {
                        CommandManager.RequerySuggested -= handler;
                    }
                }
            }
        }

        /// <summary>
        /// adds a weak reference handler
        /// </summary>
        /// <param name="handlers">the list</param>
        /// <param name="handler">the event handler</param>
        internal static void AddWeakReferenceHandler(ref List<WeakReference> handlers, EventHandler handler)
        {
            AddWeakReferenceHandler(ref handlers, handler, -1);
        }

        /// <summary>
        /// adds a weak reference handler
        /// </summary>
        /// <param name="handlers">the handlers</param>
        /// <param name="handler">the handler</param>
        /// <param name="defaultListSize">default size</param>
        internal static void AddWeakReferenceHandler(ref List<WeakReference> handlers, EventHandler handler, int defaultListSize)
        {
            if (handlers == null)
            {
                handlers = (defaultListSize > 0 ? new List<WeakReference>(defaultListSize) : new List<WeakReference>());
            }

            handlers.Add(new WeakReference(handler));
        }

        /// <summary>
        /// Removes a weak referance handler
        /// </summary>
        /// <param name="handlers">the handlers</param>
        /// <param name="handler">the handler</param>
        internal static void RemoveWeakReferenceHandler(List<WeakReference> handlers, EventHandler handler)
        {
            if (handlers != null)
            {
                for (int i = handlers.Count - 1; i >= 0; i--)
                {
                    WeakReference reference = handlers[i];
                    EventHandler existingHandler = reference.Target as EventHandler;
                    if ((existingHandler == null) || (existingHandler == handler))
                    {
                        // Clean up old handlers that have been collected
                        // in addition to the handler that is to be removed.
                        handlers.RemoveAt(i);
                    }
                }
            }
        }
        #endregion
    }
}

Very nice, man