是“使用{}"即使没有变量引用对象，也要处置它的优良作法 [英] Is "Using{}" good practice to dispose object even if there is no variable referring to it

问题描述

在我的公司中，我看到的是这样的代码

In my company, I am seeing code like this

using (LoggerFactory.GetTracer(_log.ModuleName + "._GetAccessTokenFromWns"))
{...}

当我向上看时，我发现它处理了由使用"括号内声明的变量所引用的对象.

When I looked up, I learned it disposes the objects referred by variables declared inside "Using" parenthesis.

它对上面的代码(没有指向工厂返回的对象的变量)有帮助吗?

Does it also help for code like above, where there is no variable referring to the object returned by the factory?

谢谢

推荐答案

看到您的问题后，我编写了一个简单的代码，如下所示:

After I see your question I write a simple code like this:

using (new FileStream("sample.txt",FileMode.CreateNew))
{

}

然后查看生成的IL code:

    .method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       35 (0x23)
  .maxstack  2
  .locals init ([0] class [mscorlib]System.IO.FileStream CS$3$0000,
           [1] bool CS$4$0001)
  IL_0000:  nop
  IL_0001:  ldstr      "asdas.txt"
  IL_0006:  ldc.i4.1
  IL_0007:  newobj     instance void [mscorlib]System.IO.FileStream::.ctor(string,
                                                                           valuetype [mscorlib]System.IO.FileMode)
  IL_000c:  stloc.0
  .try
  {
    IL_000d:  nop
    IL_000e:  nop
    IL_000f:  leave.s    IL_0021
  }  // end .try
  finally
  {
    IL_0011:  ldloc.0
    IL_0012:  ldnull
    IL_0013:  ceq
    IL_0015:  stloc.1
    IL_0016:  ldloc.1
    IL_0017:  brtrue.s   IL_0020
    IL_0019:  ldloc.0
    IL_001a:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_001f:  nop
    IL_0020:  endfinally
  }  // end handler
  IL_0021:  nop
  IL_0022:  ret
} // end of method Program::Main

如您所见，它仍在调用Dispose方法，它在try块之前创建FileStream实例，然后在finally中调用Dispose方法，我认为这是using语句.

As you can see it is still calling the Dispose method.It creates FileStream instance before try block, then calling the Dispose method in the finally.I think this is another advantage of using statements.

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