Problem Statement
How can a property be built, based on appending some values whose properties are in an item list.
Solutions
1. Without target batching
<Project ToolsVersion="3.5" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<ExtPath>Hello</ExtPath>
<PalPath>$(ExtPath)\PAL\v6.0</PalPath>
<MsiPath>$(ExtPath)\MSI\v3.0</MsiPath>
<WsePath>$(ExtPath)\WSE20\SP3</WsePath>
<MmcPath>$(ExtPath)\MMC\v3.0</MmcPath>
<MyConstants>Start</MyConstants>
</PropertyGroup>
<ItemGroup>
<!– Note that these properties match the names of some items –>
<ConstantsProperty Include="MsiPath" />
<ConstantsProperty Include="WsePath" />
</ItemGroup>
<Target Name="BeforeBuild">
<!– Create a new item based on properties which match item names –>
<CreateItem Include="%(Identity)=$(%(ConstantsProperty.Identity))">
<Output TaskParameter="Include" ItemName="TempMyConstants"/>
</CreateItem>
<PropertyGroup>
<!– Update the existing property –>
<MyConstants>$(MyConstants);@(TempMyConstants)</MyConstants>
</PropertyGroup>
<Message Text="BeforeBuild: MyConstants = $(MyConstants)" />
</Target>
</Project>
2. Use Target Batching, overly complex, but it works.
<Project ToolsVersion="3.5" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<ExtPath>Hello</ExtPath>
<PalPath>$(ExtPath)\PAL\v6.0</PalPath>
<MsiPath>$(ExtPath)\MSI\v3.0</MsiPath>
<WsePath>$(ExtPath)\WSE20\SP3</WsePath>
<MmcPath>$(ExtPath)\MMC\v3.0</MmcPath>
<MyConstants>Start</MyConstants>
</PropertyGroup>
<ItemGroup>
<ConstantsProperty Include="MsiPath" />
<ConstantsProperty Include="WsePath" />
</ItemGroup>
<!– 1. Use DependsOnTarget to avoid any potential scoping bugs with CallTarget –>
<Target Name="BeforeBuild" DependsOnTargets="List">
<!– 5. Redefine the property –>
<PropertyGroup>
<MyConstants>$(MyConstants);@(TempItem)</MyConstants>
</PropertyGroup>
<!– 6. Display the result –>
<Message Text="BeforeBuild: MyConstants = $(MyConstants)" />
</Target>
<!– 2. Use Target Batching to iterate through the defined ConstantsProperty Item Collection –>
<Target Name="List" Inputs="@(ConstantsProperty)" Outputs="%(Identity)">
<!– 3. Define a new property to hold the calculated string –>
<PropertyGroup>
<MyNewConstants>%(Identity)=$(%(ConstantsProperty.Identity))</MyNewConstants>
</PropertyGroup>
<!– 4. Append the new property to a new Item Collection–>
<ItemGroup>
<TempItem Include="$(MyNewConstants)"/>
</ItemGroup>
</Target>
</Project>
