编译下面这段代码的时候，提示上下问不存在p1，为什么呢，要怎样修改才能通过呢？

private void Window_Loaded_1(object sender, RoutedEventArgs e)
{
person p1 = new person();
p1.Age = 18;
p1.Name = "Hello";
txtbName.DataContext = p1;
txtbAge.DataContext = p1;
}

    private void Age_Click(object sender, RoutedEventArgs e)
    {
       p1.Age++;
    }

    private void ShowAge_Click(object sender, RoutedEventArgs e)
    {
        MessageBox.Show(p1.Age.tostring());
    }
}

p1的作用域在哪呢？仅限于Window_Loaded_1方法内部，出了这个方法p1就不存在了。下面当然提示不存在p1，