Question

这是this

的后续问题

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Using构造需要什么代码。我只是想知道使用Using构造是否会比较时钟周期更快。

Answer 1

不会有性能差异。编译器将using扩展为try / finally块。

您将看到以下两种方法编译为相同的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();
    }
}

在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＃中使用try / finally，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

Answer 2

using汇编为try / catch / finally。我真的看不出有任何语义或性能差异，只要你在手册try / catch的情况下妥善处理你的对象。

在任何情况下，请使用using，因为它会为您自动清理（实际上在finally子句中）。即使存在性能差异，也可能是最小的，以便您有更好的优化位置。

Answer 3

我必须相信使用与try / catch相比，相对于在这些构造中运行的代码而言，使用性能并没有任何差别。

Answer 4

Try / Catch / Finally更快。

1）6.638秒：使用标签
2）6.265秒：尝试/捕捉/最后

我跑了十几次。 Try / Catch / Finally总是名列前茅。

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");

哪个更快 - 使用块或Try / Catch / Finally

4 个答案: