在MessageBox問題上實現重試按鈕功能（C＃）

Question

試圖編寫一些代碼來檢索文件的文件路徑，以便稍後可以在ReadFile（）函數中使用它，但會遇到一些問題。

我的目標是實現一個MessageBox，它輸出一個錯誤消息，並帶有一個重試和關閉按鈕，這兩個功能都可以工作。

當執行下面的代碼時，它會簡單地循環try塊，並且永遠不會進入catch塊，這是我不想選擇文件或在OpenFileDialog上單擊取消時要執行的操作。

下面是我目前使用的代碼..

public static string GetFile() { 
    MyLog.Write(@"Begin OpenFileDialog Process", LogFormat.Evaluate); 
    var path = _lastFilePath != string.Empty ? _lastFilePath : GetBaseDirectory(); 
    if (path == null || !Directory.Exists(path)) 
     path = Assembly.GetExecutingAssembly().CodeBase; 

    var dialog = new OpenFileDialog { 
     InitialDirectory = path, 
     Filter = @"Text|*.txt|All|*.*", 
     RestoreDirectory = true 
    }; 

    var result = DialogResult.Retry; 
    while (result == DialogResult.Retry) { 
     try { 
      if (dialog.ShowDialog() != DialogResult.OK) { 
       MyLog.Write(@"File Retrieval was Unsuccessful", LogFormat.Result); 
      } else { 
       MyLog.Write($"FilePath: {dialog.FileName}", LogFormat.Process); 
       MyLog.Write(@"File Retrieval was Successful", LogFormat.Result); 
       _lastFilePath = Path.GetDirectoryName(dialog.FileName); 
       return dialog.FileName; 
      } 
     } catch when (result == DialogResult.Retry) { 
      MyLog.Write("No File Selected", LogFormat.Error); 
      result = MessageBox.Show(@"Please select a file..", @"No File Selected!", MessageBoxButtons.RetryCancel, MessageBoxIcon.Exclamation); 
      if (result == DialogResult.Abort) throw; 
      return null; 
     } 
    } 
    return null; 
} 

我已經嘗試了代碼適應一個similar question，但我在努力理解爲什麼邏輯是不是在我的環境中工作。

我做錯了什麼？

編輯： 使用以法蓮的回答，我能想出這似乎工作如下..

// USED TO RETRIEVE THE FILENAME IN A OPENFILEDIALOG 
public static string GetFile() { 
    MyLog.Write(@"Begin OpenFileDialog Process", LogFormat.Evaluate); 
    var path = _lastFilePath != string.Empty ? _lastFilePath : GetBaseDirectory(); 
    if (path == null || !Directory.Exists(path)) 
     path = Assembly.GetExecutingAssembly().CodeBase; 

    var dialog = new OpenFileDialog { 
     InitialDirectory = path, 
     Filter = @"Text|*.txt|All|*.*", 
     RestoreDirectory = true 
    }; 

    var result = DialogResult.Retry; 
    while (result == DialogResult.Retry) { 
     if (dialog.ShowDialog() != DialogResult.OK) { 
      MyLog.Write(@"File Retrieval was Unsuccessful", LogFormat.Result); 
      MyLog.Write("No File Selected", LogFormat.Error); 
      result = MessageBox.Show(@"Please select a file..", @"No File Selected!", MessageBoxButtons.RetryCancel, MessageBoxIcon.Exclamation); 
      if (result == DialogResult.Abort || result == DialogResult.Cancel) { break; } 
      if (result == DialogResult.Retry) { return GetFile(); } 
     } 

     MyLog.Write($"FilePath: {dialog.FileName}", LogFormat.Process); 
     MyLog.Write(@"File Retrieval was Successful", LogFormat.Result); 
     _lastFilePath = Path.GetDirectoryName(dialog.FileName); 
     return dialog.FileName; 
    } 
    return null; 
} 

Answer 1

你不需要因爲你的情況進行一個try-catch當用戶沒有使用文件對話框選擇任何東西時，沒有異常被拋出或被捕獲。

嘗試：

while (result == DialogResult.Retry) { 
     if (dialog.ShowDialog() != DialogResult.OK) { 
       MyLog.Write(@"File Retrieval was Unsuccessful", LogFormat.Result); 
       MyLog.Write("No File Selected", LogFormat.Error); 
      result = MessageBox.Show(@"Please select a file..", @"No File Selected!", MessageBoxButtons.RetryCancel, MessageBoxIcon.Exclamation); 
       if (result == DialogResult.Abort) throw; 
        return null; 
      } else { 
       MyLog.Write($"FilePath: {dialog.FileName}", LogFormat.Process); 
       MyLog.Write(@"File Retrieval was Successful", LogFormat.Result); 
       _lastFilePath = Path.GetDirectoryName(dialog.FileName); 
       return dialog.FileName; 
      } 
    }