Mobile Development with C#

Conditional Compilation

One technique you may have seen if you’ve done other cross-platform development is conditional compilation. With this method, you can tell the compiler to either include or exclude blocks of code based on compilation symbols that describe the target environment. For example, most .NET projects will define a symbol named DEBUG when the project is built in the debug configuration but not in the release configuration. If you have logging code that you only want included in debug builds, you can wrap it in a conditional expression using that symbol (see Example 3-8). When the code is parsed for compilation, any code blocks surrounded by unsatisfied conditions are stripped out, and the file is compiled as if they were never there in the first place.

Example 3-8. Using the DEBUG compiler symbol

#ifdef DEBUG
    Console.WriteLine("This is only logged in debug mode");
#endif

Keep in mind that overuse of this pattern can quickly lead to code that is very difficult to read and maintain. If you find yourself using a lot of conditional compilation, it’s very likely that the abstraction pattern might be a better route to go down. That said, it can be a very handy tool when you need to make minor adjustments in a shared file based on the target environment.

In your projects, you always have the option of defining any custom symbols you want, but in many cases, there are already standard predefined symbols you can use instead (see Table 3-1). Currently, MonoTouch does not provide ...