Import Element (MSBuild)
Imports the contents of one project file into another project file.
The following sections describe attributes, child elements, and parent elements.
The path of the project file to import. The path can include wildcards. The matching files are imported in sorted order. By using this feature, you can add code to a project just by adding the code file to a directory.
A condition to be evaluated. For more information, see MSBuild Conditions.
By using the Import element, you can reuse code that is common to many project files. This makes it easier to maintain the code because any updates you make to the shared code get propagated to all the projects that import it.
By convention, shared imported project files are saved as .targets files, but they are standard MSBuild project files. MSBuild does not prevent you from importing a project that has a different file name extension, but we recommend that you use the .targets extension for consistency.
Relative paths in imported projects are interpreted relative to the directory of the importing project. Therefore, if a project file is imported into several project files in different locations, the relative paths in the imported project file will be interpreted differently for each imported project.
All MSBuild reserved properties that relate to the project file, for example, MSBuildProjectDirectory and MSBuildProjectFile, that are referenced in an imported project are assigned values based on the importing project file.
If the imported project does not have a DefaultTargets attribute, imported projects are inspected in the order that they are imported, and the value of the first discovered DefaultTargets attribute is used. For example, if ProjectA imports ProjectB and ProjectC (in that order), and ProjectB imports ProjectD, MSBuild first looks for DefaultTargets specified on ProjectA, then ProjectB, then ProjectD, and finally ProjectC.
The schema of an imported project is identical to that of a standard project. Although MSBuild may be able to build an imported project, it is unlikely because an imported project typically does not contain information about which properties to set or the order in which to run targets. The imported project depends on the project into which it is imported to provide that information.
While conditional import statements work in command-line MSBuilds, they do not work with MSBuild in the Visual Studio integrated development environment (IDE). Conditional imports are evaluated by using the configuration and platform values that are set when the project is loaded. If changes are subsequently made that require a reevaluation of the conditionals in the project file, for example, changing the platform, Visual Studio reevaluates the conditions on properties and items, but not on imports. Because the import conditional is not reevaluated, the import is skipped.
To work around this, put conditional imports in the .targets files or put code in a conditional block such as a Choose Element (MSBuild) block.
In the .NET Framework 4, MSBuild allows wildcards in the Project attribute. When there are wildcards, all matches found are sorted (for reproducibility), and then they are imported in that order as if the order had been explicitly set.
This is useful if you want to offer an extensibility point so that someone else can import a file without requiring you to explicitly add the file name to the importing file. For this purpose, Microsoft.Common.Targets contains the following line at the top of the file.
<Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportBefore\*" Condition="'$(ImportByWildcardBeforeMicrosoftCommonTargets)' == 'true' and exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\$(MSBuildThisFile)\ImportBefore')"/>
The following example shows a project that has several items and properties and imports a general project file.
<Project DefaultTargets="Compile" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <PropertyGroup> <resourcefile>Strings.resx</resourcefile> <compiledresources> $(O)\$(MSBuildProjectName).Strings.resources </compiledresources> </PropertyGroup> <ItemGroup> <CSFile Include="*.cs" /> <Reference Include="System" /> <Reference Include="System.Data" /> </ItemGroup> <Import Project="$(CommonLocation)\General.targets" /> </Project>