Since the purpose of these COMPILER directives are to tell the compiler NOT to include code, debug code,beta code, or perhaps code that is needed by all of your end users, except say those the advertising department, i.e. #Define AdDept you want to be able include or remove them based on your needs. Without having to change your source code if for example a non AdDept merges into the AdDept. Then all that needs to be done is to include the #AdDept directive in the compiler options properties page of an existing version of the program and do a compile and wa la! the merged program's code springs alive!.

对于还没有准备好进入黄金时段的新流程，或者在发布之前不能在代码中活动的新流程，您可能还想使用声明式。

总之，我就是这么做的。

删除顶部的定义

#if DEBUG
        Console.WriteLine("Mode=Debug"); 
#else
        Console.WriteLine("Mode=Release"); 
#endif

如果您试图使用为构建类型定义的变量，您应该删除这两行…

#define DEBUG  
#define RELEASE 

．.． 这将导致#if (DEBUG)始终为真。

RELEASE也没有默认的条件编译符号。如果您想定义一个转到项目属性，单击Build选项卡，然后将RELEASE添加到General标题下的Conditional编译符号文本框中。

另一个选择是这样做……

#if DEBUG
    Console.WriteLine("Debug");
#else
    Console.WriteLine("Release");
#endif

确保在“项目生成属性”中定义了DEBUG常量。这将启用#if DEBUG。我没有看到预定义的RELEASE常量，所以这可能意味着任何不在DEBUG块中的东西都是RELEASE模式。

对Tod Thomson的答案稍加修改(私生子化?)，将其作为一个静态函数而不是一个单独的类(我希望能够从我已经包含的viewutils类中调用它)。

public static bool isDebugging() {
    bool debugging = false;

    WellAreWe(ref debugging);

    return debugging;
}

[Conditional("DEBUG")]
private static void WellAreWe(ref bool debugging)
{
    debugging = true;
}

It is worth noting here that one of the most significant differences between conditionally executing code based on #if DEBUG versus if(System.Diagnostics.Debugger.IsAttached) is that the compiler directive changes the code that is compiled. That is, if you have two different statements in an #if DEBUG/#else/#endif conditional block, only one of them will appear in the compiled code. This is an important distinction because it allows you do do things such as conditionally compile method definitions to be public void mymethod() versus internal void mymethod() depending on build type so that you can, for example, run unit tests on debug builds that will not break access control on production builds, or conditionally compile helper functions in debug builds that will not appear in the final code if they would violate security in some way should they escape into the wild. The IsAttached property, on the other hand, does not affect the compiled code. Both sets of code are in all of the builds - the IsAttached condition will only affect what is executed. This by itself can present a security issue.