public RelaySimpleCommand(Action execute, Func<bool> canExecute = null, Action<IList<ValidationError>> onValidationError = null, Action<Exception> onExecutionError = null) { execute.ThrowExceptionIfArgumentIsNull("execute"); this.execute = execute; this.canExecute = canExecute; this.onValidationError = onValidationError; this.onExecutionError = onExecutionError; }