public partial class InputBox : Form
{    
  private InputBox()
  {
    InitializeComponent();
  }

  public String getValue()
  {
    return textBox1.Text;
  }

  public static bool Show(String title,String inputTips,bool isPassword,ref String value)
  {
    InputBox ib = new InputBox();
    if (title != null)
    {
      ib.Text = title;
    }
    if (inputTips != null)
    {
      ib.label1.Text = inputTips;
    }

    if (isPassword)
    {
      ib.textBox1.PasswordChar = '*';
    }

    if (ib.ShowDialog()==DialogResult.OK)
    {
      value = ib.getValue();
      ib.Dispose();
      return true;
    }
    else
    {
      ib.Dispose();
      return false;
    }
  }
}

String value;

if (InputBox.Show("用戶輸入", "密碼：", true, ref value))
{
  //輸入成功后的操作
}