Configurations let you modify target behaviors. A configuration is just a target that sets a number of properties associated to a another target.

Classical example of configurations are debug and release. As their names suggest, they are used to configure a debug or a release build, respectively. Let's see a build file fragment that illustrates how to implement configurations:

      
<?xml version="1.0"?>

<project
  name="helloworld"
  default="run">
  ...

  <target
    name="debug"
    description="Configures a debug build">
    <property
      name="project.config"
      value="debug" />
    <property
      name="build.debug"
      value="true" />
    <property
      name="package.name"
      value="${nant.project.name}-${project.config}" />
  </target>

  <target
    name="release"
    description="Configures a release build">
    <property
      name="project.config"
      value="release" />
    <property
      name="build.debug"
      value="false" />
    <property
      name="package.name"
      value="${nant.project.name}" />
  </target>

  <target
    name="build"
    description="Builds HelloWorld">
    <mkdir dir="${build.dir}/${package.name}/bin" />
    <csc
      target="exe"
      debug="${build.debug}"
      output="${build.dir}/${package.name}/bin/helloworld.exe">
      <sources>
        <include name="*.cs" />
      </sources>
    </csc>
  </target>

  ...
</project>
      
    

Depending on which configuration is executed, the build target will behave differently. For example, the command

      
nant debug build
      
    

tells NAnt to first execute the debug target, which is actually the configuration, and then to execute the build target. The debug configuration sets the build.debug property to true, causing the build target to generate a debug version of the executable.

Appendix A, Build File Examples provides a complete example of how to implement configurations.