Adding Code Just for Debug Build with C#

It's very easy to add code that will only run for Debug builds for C# projects. The if directive is all you really need to know to do this.

Just add the following two lines to your source file:

#if DEBUG
#endif

You put the code that you want for the Debug build between those two lines. When you compile the project using the 'Debug' build configuration, the compiler will include the code between those two lines. Otherwise, they are ignored.

What if you want to include code for anything other than the Debug build? Just swap 'if DEBUG' for 'if !DEBUG' in the first line of code.

Troubleshooting

The reason why this works is that, by default, the Debug build configuration of a C# project defines the 'DEBUG' constant. If your debug-only code doesn't run when using a debug build, the problem might be in your build settings.

In Visual Studio:

• Right-click the project that you're working on
• Click 'Properties'
• Click on the 'Build' tab
• Make sure that the build configuration is set to Debug (using the dropdown menu that should be at the top of the build settings pane)
• Make sure that 'Define DEBUG constant' is checked 
• Save (Ctrl + S)

Making Your Own Special Build

Because this behavior only relies on C#'s #if directive and a preset DEBUG constant, you can easily use this to add code for any special build of your project. A good example of this is a 'Demo' build configuration. If you setup a Demo configuration for your commercial application, you can sprinkle #if directives statements throughout your code and get demo-specific (or retail-specific) functionality in your program.

The following how-to was written using Visual Studio 2013, but I think that it will work just fine if you're using VS 2008 or later.

1. Add Solution Build Configuration

This can be done through the Build > Configuration Manager... window. Click the 'Active solution configuration' then click '<New...>'. Give it a name like 'Demo'. You should probably copy settings from the Release build. Make sure that 'Create new project configurations' is unchecked unless you want to add one for each project. Click OK, but don't close the 'Configuration Manager' window.

2. Add Project Build Configuration

Look at the 'Project contexts' grid/spreadsheet. Click on the 'Configuration' cell for your project. Click '<New...>'. Give it the same name as your solution config, copy the Release build settings, and uncheck 'Create new solution configurations'. Click OK, but don't close the 'Configuration Manager' window.

3. Use the new project build configuration

Make sure that the 'Active solution configuration' is your new config (Demo).  Click on the 'Configuration' cell for your project and select your new project config. Close Configuration Manager.

4. Add the conditional compilation symbol

• Right-click the project that you're working on
• Click 'Properties'
• Click on the 'Build' tab
• Make sure that the build configuration is set to your new config (using the dropdown menu that should be at the top of the build settings pane) 
• Type your new compilation symbol in the 'Conditional compilation symbols' text box
• Save (Ctrl + S)

 

5. Use your new compilation symbol in code

If you're using 'DEMO' as the compilation symbol, sprinkle these two lines throughout your code to write build-specific code.

#if DEMO
#endif