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哪个更快-一个using块或try/catch/finally

using performance vb.net

crackedcornjimmy · 技术社区 · 16 年前

这是一个后续问题 this

我应该坚持使用try/catch/finally构造,还是使用using构造?

Try/Catch/Finally的示例代码:

Dim oRequest As WebRequest
Dim oResponse As HttpWebResponse = Nothing
Dim dataStream As Stream = Nothing
Dim reader As StreamReader = Nothing
Dim responseFromServer As String

Try
        sNewCustomerURL = NewCustomerQueryStringPrepare()

    'make the call to the webservice to add a new customer
    oRequest = WebRequest.Create(sNewCustomerURL)

    oRequest = CType(oRequesC, HttpWebRequest)
    oRequest.Method = "GET"
    oResponse = CType(oRequest.GetResponse(), HttpWebResponse)

    dataStream = oResponse.GetResponseStream()
    reader = New StreamReader(dataStream)
    responseFromServer = reader.ReadToEnd()

        Dim xml As New XmlDocument()
    xml.LoadXml(responseFromServer)
    Dim node As XmlNodeList = xml.GetElementsByTagName("SUCCESS")
    Dim value = CBool(node(0).InnerText)

    'do stuff               


Catch ex As Exception

       'process exception

Finally

    'do cleanup
    oRequest = Nothing
    If Not oResponse Is Nothing Then
        oResponse.Close()
    End If
    oResponse = Nothing
    If Not reader Is Nothing Then
        reader.Close()
    End If
    reader = Nothing
    If Not dataStream Is Nothing Then
        dataStream.Flush()
        dataStream.Close()
    End If
    dataStream = Nothing
End Try

我知道使用构造需要什么代码。我只想知道使用using结构是否比时钟周期更快。

4 回复 | 直到 14 年前

Dirk Vollmar 16 年前

不会有性能差异。 using 由编译器扩展为try/finally块。

您将看到以下两个方法编译为相同的IL。

void SampleWithUsing()
{
    using (MemoryStream s = new MemoryStream())
    {
        s.WriteByte(1);
    }
}

void SampleWithTryFinally()
{
    MemoryStream s = new MemoryStream();
    try
    {
        s.WriteByte(1);
    }
    finally
    {
        if (s != null) s.Dispose();
    }
}

第一种情况下生成的IL是:

.method private hidebysig instance void  SampleWithUsing() cil managed
{
  // Code size       26 (0x1a)
  .maxstack  2
  .locals init ([0] class [mscorlib]System.IO.MemoryStream s)
  IL_0000:  newobj     instance void [mscorlib]System.IO.MemoryStream::.ctor()
  IL_0005:  stloc.0
  .try
  {
    IL_0006:  ldloc.0
    IL_0007:  ldc.i4.1
    IL_0008:  callvirt   instance void [mscorlib]System.IO.Stream::WriteByte(uint8)
    IL_000d:  leave.s    IL_0019
  }  // end .try
  finally
  {
    IL_000f:  ldloc.0
    IL_0010:  brfalse.s  IL_0018
    IL_0012:  ldloc.0
    IL_0013:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_0018:  endfinally
  }  // end handler
  IL_0019:  ret
} // end of method Program::SampleWithUsing

在第二种情况下,在C中尝试/最终,我们得到:

.method private hidebysig instance void  SampleWithTryFinally() cil managed
{
  // Code size       26 (0x1a)
  .maxstack  2
  .locals init ([0] class [mscorlib]System.IO.MemoryStream s)
  IL_0000:  newobj     instance void [mscorlib]System.IO.MemoryStream::.ctor()
  IL_0005:  stloc.0
  .try
  {
    IL_0006:  ldloc.0
    IL_0007:  ldc.i4.1
    IL_0008:  callvirt   instance void [mscorlib]System.IO.Stream::WriteByte(uint8)
    IL_000d:  leave.s    IL_0019
  }  // end .try
  finally
  {
    IL_000f:  ldloc.0
    IL_0010:  brfalse.s  IL_0018
    IL_0012:  ldloc.0
    IL_0013:  callvirt   instance void [mscorlib]System.IO.Stream::Dispose()
    IL_0018:  endfinally
  }  // end handler
  IL_0019:  ret
} // end of method Program::SampleWithTryFinally

user438034 14 年前

using 编译成 try / catch / finally . 我真的看不出有任何语义或性能上的区别,只要你在手册的情况下正确地处理你的对象。 尝试 / 抓住 .

不管怎样,继续 使用 ,就像它自动清理一样(实际上在 最后 条款)。即使存在性能差异,它也可能非常小,以至于您有更好的地方进行优化。

E.J. Brennan 16 年前

我必须相信,相对于您在这些构造中运行的代码,使用和Try/Catch不会对性能产生任何影响。

tidwall 16 年前

Try/Catch/Finally更快。

1)6.638秒:使用标签
2)6.265秒:尝试/捕获/最终

我跑了十几次。尝试/抓住/最后总是出类拔萃。

DateTime start = DateTime.Now;
for (int i = 0; i < 50000000; i++)
{
    using (MemoryStream s = new MemoryStream())
    {
        s.WriteByte(1);
    }
}
Console.WriteLine(DateTime.Now.Subtract(start) + " seconds");
start = DateTime.Now;
for (int i = 0; i < 50000000; i++)
{
    MemoryStream s = null;
    try
    {
        s = new MemoryStream();
        s.WriteByte(1);
    }
    catch { }
    finally
    {
        if (s != null) s.Dispose();
    }
}
Console.WriteLine(DateTime.Now.Subtract(start) + " seconds");