100分求助！！！WPF 的问题 请大虾们进来看看 比较急！！！
WPF程序采用了MVVM模式编程 ，在程序设计中我需要往ICommand传window窗体参数，可是当我绑定参数后，vs2010设计器就报错，不能显示正常的设计界面，如下图


把我代码贴出来，麻烦大虾们帮忙解决
RelayCommand.cs

 public class RelayCommand<T>:ICommand
    {
        //定义执行命令成员和是否可执行命令成员
        readonly Action<T> _execute;
        readonly Func<T,bool> _canExecute;

        //构造函数
        public RelayCommand(Action<T> execute)
            : this(execute, null)
        {

        }

        public RelayCommand(Action<T> execute, Func<T,bool> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("RelayCommand执行命令不可预知");
            _execute = execute;
            _canExecute = canExecute;
        }

        public bool CanExecute(T parameter)
        {
            return _canExecute == null ? true : _canExecute(parameter);
        }

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public void Execute(T parameter)
        {
            _execute(parameter);
        }

        public bool CanExecute(object parameter)
        {
           return _canExecute == null ? true : _canExecute((T)parameter);
        }

        public void Execute(object parameter)
        {
            _execute((T)parameter);
        }
    }

ViewModelBase.cs

public abstract class ViewModelBase : INotifyPropertyChanged,IDisposable
    {
        protected ViewModelBase() { } 
 

        ~ViewModelBase() { }
 
        //属性更改事件
        public event PropertyChangedEventHandler PropertyChanged;

        

        protected virtual bool ThrowOnInvalidPropertyName
        {
            get;
            private set;
        }

        public void Dispose()
        {
            OnDispose();
        }
        protected virtual void OnDispose()
        {
        }
        protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            //this.VerifyPropertyName(propertyName);
            var hanlder = this.PropertyChanged;
            if (hanlder != null)
            {
                hanlder(this, e);
            }
        }
        /// <summary>
        /// 提示属性已更改
        /// </summary>
        /// <param name="propertyName">更改的属性名称</param>
        public void RaisePropertyChanged(string propertyName)
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
        }

        /// <summary>
        /// 提示属性已更改
        /// </summary>
        /// <typeparam name="TProperty">更改的属性类型</typeparam>
        /// <param name="expr">更改的属性表达式</param>
        public void RaisePropertyChanged<TProperty>(Expression<Func<TProperty>> expr)
        {
            MemberExpression memberExpr = (MemberExpression)expr.Body;
            string memberName = memberExpr.Member.Name;
            RaisePropertyChanged(memberName);
        }

        [Conditional("DEBUG")] 
 
        [DebuggerStepThrough]
        public void VerifyPropertyName(string propertyName)
        {
            if (TypeDescriptor.GetProperties(this)[propertyName] == null)
            {
                string msg = "无效的属性名称："+propertyName;
                if (this.ThrowOnInvalidPropertyName)
                    throw new Exception(msg);
                else
                    Debug.Fail(msg);
            }
        }
    }

MainWindwoViewModel.cs

 public class MainWindowViewModel:ViewModelBase
    {
        private ICommand _closeMainWindow;

        public ICommand CloseMainWindow
        {
            get
            {
                if (_closeMainWindow == null)
                {
                    _closeMainWindow = new RelayCommand<Window>(CloseMainWindowAction,CanCloseMainWindowAction);
                }
                return _closeMainWindow;
            }
            
        }

        private void CloseMainWindowAction(Window parameter)
        {
            if (MessageBox.Show("确定关闭客户端主窗口吗？", "长今提示", MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes)
            {
                parameter.Close();
            }
        }

        private bool CanCloseMainWindowAction(Window parameter)
        {
            return true;
        }
    }

xaml绑定代码

 
 
<Button Content="退出" Height="19" Name="BtnExit" Width="40" FontSize="14"  Margin="5,5,0,0" Style="{StaticResource LinkBtnStyle}"
                            Template="{StaticResource LinkBtnTemp}" Command="{Binding CloseMainWindow}" CommandParameter="{Binding ElementName=MainWindow}"/>

在RelayCommand代码里下图处出现的转换错误 如果直接返回True就不会有问题了，如图


求大侠指教！！！！！
[解决办法]
_canExecute((T)parameter);
里面 的参数转换失败，A类型不能转换到B类型
[解决办法]
wpf 是什么？？？？
[解决办法]
错误应该出在 _canExecute((T)parameter