How to: Use the same target in multiple project files

Artigo
11/04/2016

If you have authored several MSBuild project files, you might have discovered that you need to use the same tasks and targets in different project files. Instead of including the complete description of those tasks or targets in every project file, you can save a target in a separate project file and then import that project into any other project that needs to use the target.

Use the Import element

The Import element is used to insert one project file into another project file. The project file that is being imported must be a valid MSBuild project file and contain well-formed XML. The Project attribute specifies the path to the imported project file. For more information on the Import element, see Import element (MSBuild).

To import a project

Define, in the importing project file, all properties and items that are used as parameters for properties and items in the imported project.
Use the Import element to import the project. For example:

<Import Project="MyCommon.targets"/>
Following the Import element, define all properties and items that must override default definitions of properties and items in the imported project.

Order of evaluation

When MSBuild reaches an Import element, the imported project is effectively inserted into the importing project at the location of the Import element. Therefore, the location of the Import element can affect the values of properties and items. It is important to understand the properties and items that are set by the imported project, and the properties and items that the imported project uses.

When the project builds, all properties are evaluated first, followed by items. For example, the following XML defines the imported project file MyCommon.targets:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <PropertyGroup>
        <Name>MyCommon</Name>
    </PropertyGroup>

    <Target Name="Go">
        <Message Text="Name=$(Name)"/>
    </Target>
</Project>

The following XML defines MyApp.proj, which imports MyCommon.targets:

<Project
    DefaultTargets="Go"
    xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <PropertyGroup>
        <Name>MyApp</Name>
    </PropertyGroup>
    <Import Project="MyCommon.targets"/>
</Project>

When the project builds, the following message is displayed:

Name="MyCommon"

Because the project is imported after the property Name has been defined in MyApp.proj, the definition of Name in MyCommon.targets overrides the definition in MyApp.proj. If the project is imported before the property Name is defined, the build would display the following message:

Name="MyApp"

Use the following approach when importing projects

Define, in the project file, all properties and items that are used as parameters for properties and items in the imported project.
Import the project.
Define in the project file all properties and items that must override default definitions of properties and items in the imported project.

Example 1

The following code example shows the MyCommon.targets file that the second code example imports. The .targets file evaluates properties from the importing project to configure the build.

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <PropertyGroup>
        <Flavor Condition="'$(Flavor)'==''">DEBUG</Flavor>
        <Optimize Condition="'$(Flavor)'=='RETAIL'">yes</Optimize>
        <appname>$(MSBuildProjectName)</appname>
    <PropertyGroup>
    <Target Name="Build">
        <Csc Sources="hello.cs"
            Optimize="$(Optimize)"
            OutputAssembly="$(appname).exe"/>
    </Target>
</Project>

Example 2

The following code example imports the MyCommon.targets file.

<Project DefaultTargets="Build"
    xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <PropertyGroup>
        <Flavor>RETAIL</Flavor>
    </PropertyGroup>
    <Import Project="MyCommon.targets"/>
</Project>

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