Target Element (MSBuild)

Contains a set of tasks for MSBuild to execute sequentially.

<Project>
   <Target>
<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>

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 MSBuild 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 MSBuild 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 MSBuild 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 MSBuild 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.

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 MSBuild 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.

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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