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Work with item functions

  • Artikkeli

Code in tasks and targets can call item functions to get information about the items in the project (in MSBuild 4.0 and later). These functions simplify getting distinct items and are faster than looping through the items.

String item functions

You can use string methods and properties in the .NET Framework to operate on any item value. For String methods, specify the method name. For String properties, specify the property name after "get_".

For items that have multiple strings, the string method or property runs on each string.

The following example shows how to use these string item functions.

<ItemGroup>
    <theItem Include="andromeda;tadpole;cartwheel" />
</ItemGroup>

<Target Name = "go">
    <Message Text="IndexOf  @(theItem->IndexOf('r'))" />
    <Message Text="Replace  @(theItem->Replace('tadpole', 'pinwheel'))" />
    <Message Text="Length   @(theItem->get_Length())" />
    <Message Text="Chars    @(theItem->get_Chars(2))" />
</Target>

  <!--
  Output:
    IndexOf  3;-1;2
    Replace  andromeda;pinwheel;cartwheel
    Length   9;7;9
    Chars    d;d;r
  -->

Intrinsic item functions

The table below lists the intrinsic functions available for items.

Function Example Description
Combine @(MyItems->Combine('path')) Returns a new set of items with a given relative path appended to all the input items.
Count @(MyItems->Count()) Returns the count of the items.
DirectoryName @(MyItems->DirectoryName()) Returns the equivalent of Path.DirectoryName for each item.
Distinct @(MyItems->Distinct()) Returns items that have distinct Include values. Metadata is ignored. The comparison is case insensitive.
DistinctWithCase @(MyItems->DistinctWithCase()) Returns items that have distinct itemspec values. Metadata is ignored. The comparison is case sensitive.
Exists @(MyItems->Exists()) Filters a set of items to those that actually exist on disk.
GetPathsOfAllDirectoriesAbove @(MyItems->GetPathsOfAllFilesAbove()) Given a set of items, returns items representing all the ancestor directories. No order is guaranteed.
Reverse @(MyItems->Reverse()) Returns the items in reverse order.
AnyHaveMetadataValue @(MyItems->AnyHaveMetadataValue("MetadataName", "MetadataValue")) Returns a boolean to indicate whether any item has the given metadata name and value. The comparison is case insensitive.
ClearMetadata @(MyItems->ClearMetadata()) Returns items with their metadata cleared. Only the itemspec is retained.
HasMetadata @(MyItems->HasMetadata("MetadataName")) Returns items that have the given metadata name. The comparison is case insensitive.
Metadata @(MyItems->Metadata("MetadataName")) Returns the values of the metadata that have the metadata name. The items returned have the same metadata as the source values.
WithMetadataValue @(MyItems->WithMetadataValue("MetadataName", "MetadataValue")) Returns items that have the given metadata name and value. The comparison is case insensitive.

Note

Exists can also be used in other contexts; in MSBuild conditions, for example Condition="Exists('path')"; or in Static property functions, for example $([System.IO.File]::Exists("path")).

The following example shows how to use intrinsic item functions.

<ItemGroup>
    <TheItem Include="first">
        <Plant>geranium</Plant>
    </TheItem>
    <TheItem Include="second">
        <Plant>algae</Plant>
    </TheItem>
    <TheItem Include="third">
        <Plant>geranium</Plant>
    </TheItem>
</ItemGroup>

<Target Name="go">
    <Message Text="MetaData:    @(TheItem->Metadata('Plant'))" />
    <Message Text="HasMetadata: @(theItem->HasMetadata('Plant'))" />
    <Message Text="WithMetadataValue: @(TheItem->WithMetadataValue('Plant', 'geranium'))" />
    <Message Text=" " />
    <Message Text="Count:   @(theItem->Count())" />
    <Message Text="Reverse: @(theItem->Reverse())" />
</Target>

  <!--
  Output:
    MetaData:    geranium;algae;geranium
    HasMetadata: first;second;third
    WithMetadataValue: first;third

    Count:   3
    Reverse: third;second;first
  -->

Detecting duplicates when using the Metadata item function

The Metadata item function preserves the original metadata of the source items. This has some implications when considering whether the items returned are duplicates or not. To control how duplicate items are handled, you can use the attribute KeepDuplicates. You can also remove the metadata, if it's not needed, by adding the RemoveMetadata, in which case only the values themselves are considered when detecting duplicates.

  <Target Name="MetadataToItem">
    <ItemGroup>
      <Sample Include="AAA" SomeItems="1;2;3" />
      <Sample Include="BBB" SomeItems="3;4;5" />
    </ItemGroup>

    <ItemGroup>
      <AllSomeItems Include="@(Sample->Metadata('SomeItems'))" KeepDuplicates="false" />
    </ItemGroup>
    <Message Text="AllSomeItems is @(AllSomeItems)" />
  </Target>

The output is as follows:

MetadataToItem:
  AllSomeItems is 1;2;3;3;4;5

The following change to the code results in the duplicate item value being successfully detected and removed:

    <ItemGroup>
      <AllSomeItems Include="@(Sample->Metadata('SomeItems'))" KeepDuplicates="false" RemoveMetadata="SomeItems" />
    </ItemGroup>

MSBuild condition functions

The function HasTrailingSlash is not an item function. It is available for use with the Condition attribute. See MSBuild conditions.

Related content

You can also use attributes to perform operations on item lists, such as filtering on item metadata. For more information, see Items.