第二次调用 Form.Show（） 时出错

问：

我有一个带按钮的主窗体。

OnClick 该按钮执行以下操作...

Form AllBook = new Form();
//Does some other processing and SQLReader querying.
AllBook.Show();

之后，我关闭了表单。当我尝试再次显示它时，我收到此错误。

System.ObjectDisposedException：“无法访问已释放的对象。 对象名称：'Form'。

// objects
Form AllBook        = new Form();
ComboBox booksList  = new ComboBox();
ComboBox chapters   = new ComboBox();
Panel topPannel     = new Panel();
Panel txtPannel     = new Panel();
TextBox mainText    = new TextBox();

private void button1_Click(object sender, EventArgs e)
{
    // add objects to form
    AllBook.Controls.Add(topPannel);
    topPannel.Controls.Add(booksList);

    // get combobox items from another Method
    int chapterCount = countChapters(43);
        for (int i = 1; i <= chapterCount; i++) {
            chapters.Items.Add(i);
        }

    topPannel.Controls.Add(chapters);
    AllBook.Controls.Add(txtPannel);

    txtPannel.Controls.Add(mainText);

    AllBook.Show();
}

// count books chapters
public int countChapters(int bookNum) {
     int chapter = 0;
     switch (bookNum) {
         case 1:
            chapter = 50;
              break;
              case 2:
            chapter = 40;
              break;
              case 3:
            chapter = 27;
              break;
              case 4:
            chapter = 36;
              break;
        .....
}