为什么要在 C# 中捕获并重新抛出异常? [英] Why catch and rethrow an exception in C#?

问题描述

我正在看文章 C# - 数据传输对象 关于可序列化的 DTO.

I'm looking at the article C# - Data Transfer Object on serializable DTOs.

文章中包含了这段代码:

The article includes this piece of code:

public static string SerializeDTO(DTO dto) {
    try {
        XmlSerializer xmlSer = new XmlSerializer(dto.GetType());
        StringWriter sWriter = new StringWriter();
        xmlSer.Serialize(sWriter, dto);
        return sWriter.ToString();
    }
    catch(Exception ex) {
        throw ex;
    }
}

文章的其余部分看起来很理智和合理(对于菜鸟来说)，但是 try-catch-throw 会抛出 WtfException... 这不完全等同于根本不处理异常吗?

The rest of the article looks sane and reasonable (to a noob), but that try-catch-throw throws a WtfException... Isn't this exactly equivalent to not handling exceptions at all?

尔格:

public static string SerializeDTO(DTO dto) {
    XmlSerializer xmlSer = new XmlSerializer(dto.GetType());
    StringWriter sWriter = new StringWriter();
    xmlSer.Serialize(sWriter, dto);
    return sWriter.ToString();
}

或者我是否遗漏了一些关于 C# 中错误处理的基本知识?它与 Java 几乎相同(减去检查的异常)，不是吗?...也就是说，他们都改进了 C++.

Or am I missing something fundamental about error handling in C#? It's pretty much the same as Java (minus checked exceptions), isn't it? ... That is, they both refined C++.

堆栈溢出问题重新抛出无参数捕获和不做任何事情之间的区别? 似乎支持我的论点，即 try-catch-throw 是无操作的.

The Stack Overflow question The difference between re-throwing parameter-less catch and not doing anything? seems to support my contention that try-catch-throw is-a no-op.

只是为以后发现这个帖子的人总结一下......

Just to summarise for anyone who finds this thread in future...

不要

try {
    // Do stuff that might throw an exception
}
catch (Exception e) {
    throw e; // This destroys the strack trace information!
}

堆栈跟踪信息对于确定问题的根本原因至关重要！

The stack trace information can be crucial to identifying the root cause of the problem!

做

try {
    // Do stuff that might throw an exception
}
catch (SqlException e) {
    // Log it
    if (e.ErrorCode != NO_ROW_ERROR) { // filter out NoDataFound.
        // Do special cleanup, like maybe closing the "dirty" database connection.
        throw; // This preserves the stack trace
    }
}
catch (IOException e) {
    // Log it
    throw;
}
catch (Exception e) {
    // Log it
    throw new DAOException("Excrement occurred", e); // wrapped & chained exceptions (just like java).
}
finally {
    // Normal clean goes here (like closing open files).
}

在不太具体的异常之前捕获更具体的异常(就像 Java).

Catch the more specific exceptions before the less specific ones (just like Java).

参考:

• MSDN - 异常处理
• MSDN - try-catch(C# 参考)

推荐答案

First;文章中的代码这样做的方式是邪恶的.throw ex 会将异常中的调用堆栈重置到该 throw 语句所在的位置；丢失有关异常实际创建位置的信息.

First; the way that the code in the article does it is evil. throw ex will reset the call stack in the exception to the point where this throw statement is; losing the information about where the exception actually was created.

其次，如果你只是像这样捕获并重新抛出，我认为没有任何附加值，上面的代码示例会一样好(或者，考虑到 throw ex 位，甚至更好)没有 try-catch.

Second, if you just catch and re-throw like that, I see no added value, the code example above would be just as good (or, given the throw ex bit, even better) without the try-catch.

但是，在某些情况下，您可能希望捕获并重新抛出异常.日志记录可能是其中之一:

However, there are cases where you might want to catch and rethrow an exception. Logging could be one of them:

try 
{
    // code that may throw exceptions    
}
catch(Exception ex) 
{
    // add error logging here
    throw;
}

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