如何在codebehind中访问CommandParameter？

<Button Content="Click Me" Command="{Binding MyCommand}" CommandParameter="{Binding SomeProperty}" />

public object SomeProperty { get; set; }

public MyPage()
{
    InitializeComponent();
    DataContext = this;
}

private void MyCommandExecute(object parameter)
{
    // 使用CommandParameter的值
    var param = parameter as SomeType;
    // ...
}