How to Implement Effective Exception Handling Best Practices?

Best Exception Handling Practices

Code reviews often reveal that exception handling is implemented in an inefficient manner, raising concerns about whether these practices are consistent with industry best practices.

Problem Description

Some code snippets showing questionable exception handling:

<code>try
{
  //执行某些操作
}
catch
{
  //什么也不做
}</code>

Or record information in try-catch block, for example:

<code>try
{
  //执行某些工作
}
catch(Exception exception)
{
   WriteException2LogFile(exception);
}</code>

Best Practice Guidelines

A well-designed exception handling strategy should follow the following guidelines:

• Catch unhandled exceptions: Connect to the Application.ThreadException event to catch all unhandled exceptions.
• All external code should be enclosed in a try-catch block: Enclose any externally executed code (events, third-party components) in a try-catch block.
• Handle known potential errors: Wrap error-prone operations (IO operations, divide by zero) in try-catch blocks. Throws a custom exception with a detailed message.
• Classify exceptions: Group exceptions based on severity and whether they require immediate user notification, additional handling, or logging.
• Centralize handling of exceptions: Design static methods for exception handling in advanced error handlers.
• Bubble errors upward: All exceptions should bubble up to the top level to avoid redundant exception handling.

Code Example

Bad Practice:

<code>// 不要这样做，这是错误的。
try
{
    ...
}
catch 
{
   // 空的catch块。
}</code>

Invalid practice:

<code>// 也不要这样做。
try
{
    ...
}
catch(Exception ex)
{
    throw ex;
}</code>

Valid usage:

<code>try
{
    listView1.BeginUpdate();

    // 异常处理代码...
}
finally
{
    // 保证执行。
    listView1.EndUpdate();
}</code>

Advanced processing:

<code>try
{
    ...
}
catch(Exception ex)
{
    ex.Log(); // 记录异常。

    // 或者：
    ex.Log().Display(); // 记录异常并显示给用户。
}</code>

Function level processing:

<code>// 计算模块
try
{
    ...
}
catch(Exception ex)
{
    throw new ApplicationException("计算模块错误。", ex);
}

// IO模块
try
{
    ...
}
catch(Exception ex)
{
    throw new ApplicationException("文件写入错误。", ex);
}</code>

Extension methods:

<code>// 用法：

try
{
    // 错误处理...
}
catch(Exception ex)
{
    // 只记录日志。
    ex.Log();

    // 只显示。
    ex.Display();

    // 先记录日志，再显示。
    ex.Log().Display();

    // 添加自定义用户消息。
    new ApplicationException("无法计算。", ex).Log().Display();
}

// 扩展方法：

internal static Exception Log(this Exception ex)
{
    // 记录异常。
    return ex;
}

internal static Exception Display(this Exception ex, string msg = null, MessageBoxImage img = MessageBoxImage.Error)
{
    // 显示异常。
    return ex;
}</code>

Following these best practices ensures that exceptions are handled effectively, providing users and developers with necessary information while maintaining application stability and reliability.

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