Ribbon Command Binding With TypeSafe Commands.

 /// <summary>
        /// Determines whether the save command can execute.
        /// </summary>
        /// <param name="parameter">The parameter.</param>
        /// <returns>
        ///     <c>true</c> if this instance [can save execute] the specified parameter; otherwise, <c>false</c>.
        /// </returns>
        public virtual bool CanSaveExecute(SaveCommandParameter parameter)
        {
            return true;
        }

bool ICommand.CanExecute(object parameter)
{
    // if T is of value type and the parameter is not
    // set yet, then return false if CanExecute delegate
    // exists, else return true
    if (parameter == null &&
        typeof(T).IsValueType)
    {
        return this.canExecuteMethod == null;
    }

    return this.CanExecute((T)parameter);
}

bool ICommand.CanExecute(object parameter)
{
    // If T is a value type...
    if (typeof(T).IsValueType) {
        // If there is no parameter, or parameter is not a value type, or parameter is not the same value type, quit
        if ((parameter == null) || (!parameter.GetType().IsValueType) || (parameter.GetType() != typeof(T)))
            return false;
    }
    else {
        // T is not a value type... ensure a cast will work
        if (!typeof(T).IsInstanceOfType(parameter))
            return false;
    }

    return this.CanExecute((T)parameter);
}

<ribbon:Button
   Label="ribbon:Button"
   Command="{Binding TestCommand}"
   CommandParameter="{x:Type ribbon:Button}"
   />

if (parameter is ActiproSoftware.Windows.Controls.Ribbon.Input.CheckableCommandParameter)
    return this.CanExecute(default(T));

return this.CanExecute(parameter as T);

        /// <summary>
        /// ICommand.CanExecute implemenation
        /// </summary>
        /// <param name="parameter">Object to test</param>
        /// <returns>Boolean can execute</returns>
        bool ICommand.CanExecute(object parameter)
        {
            // if T is of value type and the parameter is not
            // set yet, then return false if CanExecute delegate
            // exists, else return true
            if (parameter == null &&
                typeof(T).IsValueType)
            {
                return this.canExecuteMethod == null;
            }
            else if (!(parameter is T))
            {
                parameter = null;
            }

            return this.CanExecute((T)parameter);
        }
        /// <summary>
        /// ICommand.Execute implemenation
        /// </summary>
        /// <param name="parameter">Object to test</param>
        void ICommand.Execute(object parameter)
        {
            if (!(parameter is T))
            {
                parameter = null;
            }

            this.Execute((T)parameter);
        }