尝试/最后阻止vs调用处置？ [英] Try/Finally block vs calling dispose?

问题描述

这两个代码示例之间是否有区别，如果没有，为什么存在使用？

Is there any difference between these two code samples and if not, why does using exist?

StreamWriter writer;
try {
    writer = new StreamWriter(...)
    writer.blahblah();

} finally {
    writer.Dispose();
}

vs：

using (Streamwriter writer = new Streamwriter(...)) {
    writer.blahblah
}

我的意思是，在第二个示例中，无论如何，您实际上都应该将其放在try块中，因此添加finally块确实不会花费太多精力。我知道整个内容可能包含在更大的try块中，但是，对我来说似乎是多余的。

I mean in the second example you really should be putting it in a try block anyway so adding the finally block really doesn't use much more effort. I get that the entire thing might be encompassed in a bigger try block but yeah, just seems superfluous to me.

推荐答案

有关于您的代码一些问题。 从不这样写（改为使用），而这就是为什么：

There're some issues with your code. Never write like this (put using instead), and that's why:

StreamWriter writer;
try {
    // What if you failed here to create StreamWriter? 
    // E.g. you haven't got permissions, the path is wrong etc. 
    // In this case "writer" will point to trash and
    // The "finally" section will be executed
    writer = new StreamWriter(...) 
    writer.blahblah();
} finally {
    // If you failed to execute the StreamWriter's constructor
    // "writer" points to trash and you'll probably crash with Access Violation
    // Moreover, this Access Violation will be an unstable error!
    writer.Dispose(); 
}

当您像这样使用时

  using (StreamWriter writer = new StreamWriter(...)) {
    writer.blahblah();
  }

等于代码

StreamWriter writer = null; // <- pay attention to the assignment

try {
  writer = new StreamWriter(...) 
  writer.blahblah();
}
finally {
  if (!Object.ReferenceEquals(null, writer)) // <- ... And to the check
    writer.Dispose();
}

这篇关于尝试/最后阻止vs调用处置？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！