C#将长if语句转换为更合适的语句

Question

我有一个MDI form，其中一些子窗体需要在关闭前显示消息框，而其他窗体则可以在没有询问的情况下关闭。由于从子窗体的close event调用application.Exit()时出现问题，我处理父窗体的close event并检查它的触发位置。如果它是在需要消息框的窗体中触发的，我会调用它，否则只需关闭应用程序即可。所有这些都在下面的代码中实现：

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            SEdit se       = this.ActiveMdiChild as SEdit;
            SoEdit soleEdit = this.ActiveControl as SoEdit;
            UppEdit ue      = this.ActiveControl as UpEdit;
            MEdit mat  = this.ActiveControl as MEdit;
            LEdit lse      = this.ActiveControl as LEdit;
            CEdit cle    = this.ActiveControl as CEdit;

            if (se != null || soleEdit != null || ue != null || mat != null || lse != null || cle != null)
            {
                if (MessageBox.Show("Do you want to save before exit?", "Closing",
                      MessageBoxButtons.YesNo,
                      MessageBoxIcon.Information) == DialogResult.Yes)
                {
                    MessageBox.Show("To Do saved.", "Status",
                              MessageBoxButtons.OK,
                              MessageBoxIcon.Information);
                }
            }
         }

我还在学习，但我知道这么长的if语句是糟糕代码的标志，但我不知道如何改进它。处理这种情况的正确方法是什么？

Answer 1

提取条件以分离方法：

private bool AnyChildAlive()
{
   return (this.ActiveMdiChild is SEdit) ||
          (this.ActiveControl is SoEdit) ||
          ...
          (this.ActiveControl is CEdit);
}

然后调用此方法(也使用保护条件以避免嵌套的if语句)：

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{          
    if (!AnyChildAlive())
       return;

    if (MessageBox.Show("Do you want to save before exit?", "Closing",
           MessageBoxButtons.YesNo, 
           MessageBoxIcon.Information) != DialogResult.Yes)
       return;

   MessageBox.Show("To Do saved.", "Status",
        MessageBoxButtons.OK, MessageBoxIcon.Information);     

}

Answer 2

可能最好的方法是创建一个接口，如下所示：

public interface IFormActions {
  bool AskBeforeClosing();
  void SaveData();
}

然后，为每个表单实现该接口，并在MainForm_FormClosing方法中执行以下操作：

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
  IFormActions se = this.ActiveControl as IFormActions;
  if ((se != null) && se.AskBeforeClosing()) {
    if (MessageBox.Show("Do you want to save before exit?", "Closing", MessageBoxButtons.YesNo,  MessageBoxIcon.Information) == DialogResult.Yes) {
      se.SaveData();
      MessageBox.Show("Saved", "Status", MessageBoxButtons.OK, MessageBoxIcon.Information);
    }
  }
}

由于这段代码的编写方式，您不必为所有表单实现接口，只需为那些您实际想要提出结束语的表单实现接口即可。

Answer 3

为了让它看起来更吸引人或者是更好的重用，你可以考虑将你的验证转移到不同的方法上。

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
{
    if (FormIsValid())
    {
        if (MessageBox.Show("Do you want to save before exit?", "Closing",
              MessageBoxButtons.YesNo,
              MessageBoxIcon.Information) == DialogResult.Yes)
        {
            MessageBox.Show("To Do saved.", "Status",
                      MessageBoxButtons.OK,
                      MessageBoxIcon.Information);
        }
    }
}

private bool FormIsValid()
{
    return 
    (this.ActiveMdiChild as SEdit) != null ||
    (this.ActiveControl as SoEdit) != null ||
    (this.ActiveControl as UpEdit) != null ||
    (this.ActiveControl as MEdit)  != null ||
    (this.ActiveControl as LEdit)  != null ||
    (this.ActiveControl as CEdit)  != null;
}