c# - 哪种编码更有效: reusing variable vs writing same code twice?

Question

让我给您2种编码方式:

一种)

Console.WriteLine(String.Format("Error: {0}", genericException.Message));
SomeTextFileLogMethod(String.Format("Error: {0}", genericException.Message));

B)

var errorMessage = "String.Format("Error: {0}", genericException.Message)";
Console.WriteLine(errorMessage);
SomeTextFileLogMethod(errorMessage);

Answer 1

从直觉上讲，两次调用String.Format将产生两倍的运营成本。在此演示中，您可以看到由代码生成的中间语言，与您正在执行的操作类似。您可以看到then ...之后完成了两次“工作”。区别是微小的。而且编译器可以进行不明显的优化，因此，如果对性能有合理的考虑，则始终建议进行基准测试。

如果您真的想编写有效的日志记录和消息传递代码，建议您使用为此设计的库。可以将Serilog之类的东西配置为写入多个“接收器”。因此，一个记录消息的调用可以转到控制台，文件，电子邮件，http端点等。

string msg = string.Format("Error: {0}", "test");

Console.WriteLine(msg);
Debug.WriteLine(msg);

Debug.Write("then...");

Console.WriteLine(string.Format("Error: {0}", "test"));
Debug.WriteLine(string.Format("Error: {0}", "test"));

IL_0000:  nop         
IL_0001:  ldstr       "Error: {0}"
IL_0006:  ldstr       "test"
IL_000B:  call        System.String.Format
IL_0010:  stloc.0     // msg
IL_0011:  ldloc.0     // msg
IL_0012:  call        System.Console.WriteLine
IL_0017:  nop         
IL_0018:  ldloc.0     // msg
IL_0019:  call        System.Diagnostics.Debug.WriteLine
IL_001E:  nop         
IL_001F:  ldstr       "then..."
IL_0024:  call        System.Diagnostics.Debug.Write
IL_0029:  nop         
IL_002A:  ldstr       "Error: {0}"
IL_002F:  ldstr       "test"
IL_0034:  call        System.String.Format
IL_0039:  call        System.Console.WriteLine
IL_003E:  nop         
IL_003F:  ldstr       "Error: {0}"
IL_0044:  ldstr       "test"
IL_0049:  call        System.String.Format
IL_004E:  call        System.Diagnostics.Debug.WriteLine
IL_0053:  nop         
IL_0054:  ret