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How to: Use Build Events in MSBuild Projects

A build event is a command that MSBuild performs at a particular stage in the build process. The pre-build event occurs before the build starts; the pre-link event occurs before the link step starts; and the post-build event occurs after the build successfully ends. A build event occurs only if the associated build step occurs. For example, the pre-link event does not occur if the link step does not run.

Each of the three build events is represented in an item definition group by a command element (<Command>) that is executed and a message element (<Message>) that is displayed when MSBuild performs the build event. Each element is optional, and if you specify the same element multiple times, the last occurrence takes precedence.

An optional use-in-build element (<build-eventUseInBuild>) can be specified in a property group to indicate whether the build event is executed. The value of the content of a use-in-build element is either true or false. By default, a build event is executed unless its corresponding use-in-build element is set to false.

The following table lists each build event XML element:

XML Element

Description

PreBuildEvent

This event executes before the build begins.

PreLinkEvent

This event executes before the link step begins.

PostBuildEvent

This event executes after the build finishes.

The following table lists each use-in-build element:

XML Element

Description

PreBuildEventUseInBuild

Specifies whether to execute the pre-build event.

PreLinkEventUseInBuild

Specifies whether to execute the pre-link event.

PostBuildEventUseInBuild

Specifies whether to execute the post-build event.

The following example can be added inside of the Project element of the myproject.vcxproj file created in Walkthrough: Using MSBuild to Create a Visual C++ Project. A pre-build event makes a copy of main.cpp; a pre-link event makes a copy of main.obj; and a post-build event makes a copy of myproject.exe. If the project is built using a release configuration, the build events are executed. If the project is built using a debug configuration, the build events are not executed.

  <ItemDefinitionGroup>
    <PreBuildEvent>
      <Command>copy $(ProjectDir)main.cpp $(ProjectDir)copyOfMain.cpp</Command>
      <Message>Making a copy of main.cpp </Message>
    </PreBuildEvent>
    <PreLinkEvent>
   <Command>copy $(ProjectDir)$(Configuration)\main.obj $(ProjectDir)$(Configuration)\copyOfMain.obj</Command>
      <Message>Making a copy of main.obj</Message>
    </PreLinkEvent>
    <PostBuildEvent>
   <Command>copy $(ProjectDir)$(Configuration)\$(TargetFileName) $(ProjectDir)$(Configuration)\copyOfMyproject.exe</Command>
      <Message>Making a copy of myproject.exe</Message>
    </PostBuildEvent>
  </ItemDefinitionGroup>
 
  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
    <PreBuildEventUseInBuild>true</PreBuildEventUseInBuild>
    <PreLinkEventUseInBuild>true</PreLinkEventUseInBuild>
    <PostBuildEventUseInBuild>true</PostBuildEventUseInBuild>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
    <PreBuildEventUseInBuild>false</PreBuildEventUseInBuild>
    <PreLinkEventUseInBuild>false</PreLinkEventUseInBuild>
    <PostBuildEventUseInBuild>false</PostBuildEventUseInBuild>
  </PropertyGroup>
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