Can I make a constant from a compile-time env variable in csharp?

问题

We use Hudson to build our projects, and Hudson conveniently defines environment variables like "%BUILD_NUMBER%" at compile time.

I'd like to use that variable in code, so we can do things like log what build this is at run time. However I CAN NOT do System.Environment.GetEnvironmentVariable because that is accessing the run-time environment, what I want is something like:

#define BUILD_NUM = %BUILD_NUMBER%

const string BUILD_NUM = %BUILD_NUMBER%

Except I don't know the syntax. Can someone please point me in the right direction? Thanks!

回答1:

Okay here's what I wound up doing. It's not very elegant, but it works. I created a pre-build step that looks like this:

echo namespace Some.Namespace > "$(ProjectDir)\CiInfo.cs"
echo { >> "$(ProjectDir)\CiInfo.cs"
echo     ///^<summary^>Info about the continuous integration server build that produced this binary.^</summary^> >> "$(ProjectDir)\CiInfo.cs"
echo     public static class CiInfo >> "$(ProjectDir)\CiInfo.cs"
echo     { >> "$(ProjectDir)\CiInfo.cs"
echo         ///^<summary^>The current build number, such as "153"^</summary^> >> "$(ProjectDir)\CiInfo.cs"
echo         public const string BuildNumber = ("%BUILD_NUMBER%" == "" ? @"Unknown" : "%BUILD_NUMBER%"); >> "$(ProjectDir)\CiInfo.cs"
echo         ///^<summary^>String of the build number and build date/time, and other useful info.^</summary^> >> "$(ProjectDir)\CiInfo.cs"
echo         public const string BuildTag = ("%BUILD_TAG%" == "" ? @"nohudson" : "%BUILD_TAG%") + " built: %DATE%-%TIME%"; >> "$(ProjectDir)\CiInfo.cs"
echo     } >> "$(ProjectDir)\CiInfo.cs"
echo } >> "$(ProjectDir)\CiInfo.cs"

Then I added "CiInfo.cs" to the project, but ignored it from version control. That way I never have to edit it or commit it, and the project always has a constant available that is the latest build number and time.

回答2:

One way to do it is to add a build-step before compilation which does a regex replace in the appropriate source file(s) for %BUILD_NUMBER%.

回答3:

One possibility is to use T4 to generate your configuration class with all the constants instantiated. T4 is well-integrated into MSVS, no need for your own custom build step.

回答4:

define does not allow you to define contants in C# like you can in C/C++.

From this page:

The #define directive cannot be used to declare constant values as is typically done in C and C++. Constants in C# are best defined as static members of a class or struct. If you have several such constants, consider creating a separate "Constants" class to hold them.

If you are looking to reflect the build number in you AssemblyInfo class, most build tools support generating that class at build time. MSBuild has a task for it. As does NAnt. Not sure how Hudson does this.

来源：https://stackoverflow.com/questions/4450231/can-i-make-a-constant-from-a-compile-time-env-variable-in-csharp

标签

environment-variables

compile-time