Question

What is the difference between creating an item inside a target like this:

<Target Name="DoStuff">
    <CreateItem Include="@(IntermediateAssembly)" >
        <Output TaskParameter="Include" ItemName="FileWrites"/>
    </CreateItem>
</Target>

and like this:

<Target Name="DoStuff">
    <ItemGroup>
        <FileWrites Include="@(IntermediateAssembly)" />
    </ItemGroup>
</Target>

When would you use one or the other and why?

Answer 1

In versions of MSBuild prior to 3.5 you could not define properties or items inside of targets (like in your second example). So a task was used instead (CreateItem and CreateProperty)

If you are using ToolsVersion 3.5 then you don’t need to use CreateItem anymore (though you still can if you prefer).

In the end they both create the item the same, with the same scope. Using the second syntax is more readable and setting up custom meta data is much easier (in my opinion).

NOTE: The 3.5 version of MSBuild is installed with .NET 3.5. Though you need to define ToolsVersion="3.5" in the Project tag of your MSBuild file to use 3.5 features.

In case you are wondering, I got most of this info from the book Inside the Microsoft® Build Engine: Using MSBuild and Team Foundation Build which I really liked (but am not affiliated with in any way).