Target Element (MSBuild)

Artikel
11/15/2016

Note

This article applies to Visual Studio 2015. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Contains a set of tasks for MSBuild to execute sequentially.

Syntax

<Target Name="Target Name"  
        Inputs="Inputs"  
        Outputs="Outputs"  
        Returns="Returns"  
        KeepDuplicateOutputs="true/false"  
        BeforeTargets="Targets"  
        AfterTargets="Targets"  
        DependsOnTargets="DependentTarget"  
        Condition="'String A' == 'String B'">  
        Label="Label">  
    <Task>... </Task>  
    <PropertyGroup>… </PropertyGroup>  
    <ItemGroup>… </ItemGroup>  
    <OnError... />  
</Target>

Attributes and Elements

The following sections describe attributes, child elements, and parent elements.

Attributes

Attribute	Description
`Name`	Required attribute. The name of the target.
`Condition`	Optional attribute. The condition to be evaluated. If the condition evaluates to `false`, the target will not execute the body of the target or any targets that are set in the `DependsOnTargets` attribute. For more information about conditions, see Conditions.
`Inputs`	Optional attribute. The files that form inputs into this target. Multiple files are separated by semicolons. The timestamps of the files will be compared with the timestamps of files in `Outputs` to determine whether the `Target` is up to date. For more information, see Incremental Builds, How to: Build Incrementally, and Transforms.
`Outputs`	Optional attribute. The files that form outputs into this target. Multiple files are separated by semicolons. The timestamps of the files will be compared with the timestamps of files in `Inputs` to determine whether the `Target` is up to date. For more information, see Incremental Builds, How to: Build Incrementally, and Transforms.
`Returns`	Optional attribute. The set of items that will be made available to tasks that invoke this target, for example, MSBuild tasks. Multiple targets are separated by semicolons. If the targets in the file have no `Returns` attributes, the Outputs attributes are used instead for this purpose.
`KeepDuplicateOutputs`	Optional Boolean attribute. If `true`, multiple references to the same item in the target's Returns are recorded. By default, this attribute is `false`.
`BeforeTargets`	Optional attribute. A semicolon-separated list of target names. When specified, indicates that this target should run before the specified target or targets. This lets the project author extend an existing set of targets without modifying them directly. For more information, see Target Build Order.
`AfterTargets`	Optional attribute. A semicolon-separated list of target names. When specified, indicates that this target should run after the specified target or targets. This lets the project author extend an existing set of targets without modifying them directly. For more information, see Target Build Order.
`DependsOnTargets`	Optional attribute. The targets that must be executed before this target can be executed or top-level dependency analysis can occur. Multiple targets are separated by semicolons.
`Label`	Optional attribute. An identifier that can identify or order system and user elements.

Child Elements

Element	Description
Task	Creates and executes an instance of an MSBuild task. There may be zero or more tasks in a target.
PropertyGroup	Contains a set of user-defined `Property` elements. Starting in the .NET Framework 3.5, a `Target` element may contain `PropertyGroup` elements.
ItemGroup	Contains a set of user-defined `Item` elements. Starting in the .NET Framework 3.5, a `Target` element may contain `ItemGroup` elements. For more information, see Items.
OnError	Causes one or more targets to execute if the `ContinueOnError` attribute is ErrorAndStop (or `false`) for a failed task. There may be zero or more `OnError` elements in a target. If `OnError` elements are present, they must be the last elements in the `Target` element. For information about the `ContinueOnError` attribute, see Task Element (MSBuild).

Parent Elements

Element	Description
Project	Required root element of an MSBuild project file.

Remarks

The first target to execute is specified at run time. Targets can have dependencies on other targets. For example, a target for deployment depends on a target for compilation. The MSBuild engine executes dependencies in the order in which they appear in the DependsOnTargets attribute, from left to right. For more information, see Targets.

A target is only executed once during a build, even if more than one target has a dependency on it.

If a target is skipped because its Condition attribute evaluates to false, it can still be executed if it is invoked later in the build and its Condition attribute evaluates to true at that time.

Before MSBuild 4, Target returned any items that were specified in the Outputs attribute. To do this, MSBuild had to record these items in case tasks later in the build requested them. Because there was no way to indicate which targets had outputs that callers would require, MSBuild accumulated all items from all Outputs on all invoked Targets. This lead to scaling problems for builds that had a large number of output items.

If the user specifies a Returns on any Target element in a project, then only those Targets that have a Returns attribute record those items.

A Target may contain both an Outputs attribute and a Returns attribute. Outputs is used with Inputs to determine whether the target is up-to-date. Returns, if present, overrides the value of Outputs to determine which items are returned to callers. If Returns is not present, then Outputs will be made available to callers except in the case described earlier.

Before MSBuild 4, any time that a Target included multiple references to the same item in its Outputs, those duplicate items would be recorded. In very large builds that had a large number of outputs and many project interdependencies, this would cause a large amount of memory to be wasted because the duplicate items were not of any use. When the KeepDuplicateOutputs attribute is set to true, these duplicates are recorded.

Example

The following code example shows a Target element that executes the Csc task.

<Target Name="Compile" DependsOnTargets="Resources" Returns="$(TargetPath)">  
    <Csc Sources="@(CSFile)"  
          TargetType="library"  
          Resources="@(CompiledResources)"  
          EmitDebugInformation="$(includeDebugInformation)"  
          References="@(Reference)"  
          DebugType="$(debuggingType)" >  
        <Output TaskParameter="OutputAssembly"  
                  ItemName="FinalAssemblyName" />  
    </Csc>  
</Target>

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