NuGet Warning NU1504

Scenario 1

Duplicate 'PackageReference' items found. Remove the duplicate items or use the Update functionality to ensure a consistent restore behavior. The duplicate 'PackageReference' items are: X 1.0.0, X 2.0.0.

Issue

Sometimes when adding PackageReference items, you may end up adding an item for a particular package multiple times.

Example:

<ItemGroup>
  <PackageReference Include="X" Version="1.0.0" />
</ItemGroup>
...
<!-- Somewhere else in the project file, or another MSBuild file-->
<ItemGroup>
  <PackageReference Include="X" Version="2.0.0" />
</ItemGroup>

This can cause an inconsistent restore behavior.

Solution

Consult the recommendations in the warning message and do one of the following:

• Remove the duplicate items
• Use item Update instead of item Include