（Visual Studio）如果编译为项目，构建时间会更长，如果单独编译，则构建时间会更短

Question

我有一个cpp文件，如果我只是右键单击并在Visual Studio上编译它需要大约10秒钟编译，但是在编译为项目时需要花费大量时间（这个cpp文件在20中是1）其他）。

单独编译：

1>------ Build started: Project: Xcp.Test.Boost, Configuration: Release x64 ------
1>  XcpOnEthernetDisconnectSendTest.cpp
1>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c1xx.dll)=5.196s
1>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=5.826s
1>

编译项目：

21>  XcpOnEthernetDisconnectSendTest.cpp
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c1xx.dll)=4.693s
21>  Generating Code...
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=5.204s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=6.736s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=4.203s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=2.118s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=1.980s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=1.711s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=1.547s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=2.327s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=2.410s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=5.140s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=4.439s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=5.175s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=6.389s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=3.393s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=2.289s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=0.341s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=2.098s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=1.083s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=0.399s
21>  time(C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64\c2.dll)=0.006s

另外，我没有看到其他文件的多个编译时结果，但是对于这个特定的文件。有人可以解释一下吗？