/// <summary>
/// 进入还书界面
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnReturn_Click(object sender, EventArgs e)
{
this.Hide();
int stock = 0;
if(!txtStock.Text.Equals(""))
{
stock = Convert.ToInt32(txtStock.Text.ToString());
}
ReturnBook returnBook = new ReturnBook(correctID, stock,this);
returnBook.Show();
}