*.targets cannot be imported again. It was already imported

Question

I have UWP app build in VS 2017 and many project in my solution have build warning like below. How to get rid of them?

Warning "C:\Program Files (x86)\MSBuild\15.0.Net\CoreRuntime\Microsoft.Net.CoreRuntime.targets" cannot be imported again. It was already imported at "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\15.0\Microsoft.Common.targets\ImportAfter\Microsoft.Net.CoreRuntime.ImportAfter.targets (17,3)". This is most likely a build authoring error. This subsequent import will be ignored. [D:\Projects\HA4IoT\Controllers\HA4IoT.Controller\HA4IoT.Service.csproj] HA4IoT.Tests
Warning "C:\Program Files (x86)\MSBuild\15.0.Net\CoreRuntime\Microsoft.Net.CoreRuntime.Settings.targets" cannot be imported again. It was already imported at "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\15.0\Microsoft.Common.targets\ImportBefore\Microsoft.Net.CoreRuntime.ImportBefore.targets (17,3)". This is most likely a build authoring error. This subsequent import will be ignored. [D:\Projects\HA4IoT\DNF\HA4IoT.Extensions.Tests\HA4IoT.Extensions.Tests.csproj] HA4IoT.Controller.Dnf
Warning "C:\Users\dnf.nuget\packages\microsoft.net.native.compiler\1.6.3\tools\Microsoft.NetNative.targets" cannot be imported again. It was already imported at "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\15.0\Microsoft.Common.targets\ImportAfter\Microsoft.NetNative.ImportAfter.targets (16,3)". This is most likely a build authoring error. This subsequent import will be ignored. [D:\Projects\HA4IoT\Controllers\Examples\HA4IoT.Controller.Main\HA4IoT.Controller.Main.csproj] HA4IoT.Controller.Main

Answer 1

How to get rid of them?

I found the work-around of this question on MSDN:

Using condition to check the existence of a unique property defined in the considering project file.

<PropertyGroup>
  <TasksTargetsImported>true</TasksTargetsImpor‌​ted>
</PropertyGroup>

<Import Project="Tasks.targets" Condition=" '$(TasksTargetsImported)' == '' "/> 

Hope this can helps.

Answer 2

I removed all nuget target and prop files next to the .csproj files. This worked for me. All warnings are now gone.

Answer 3

Unload project or edit project solution file then check entire project file and make sure the same line is not repeated twice. In my case after I followed Web.config transformation instructions I added an extra line like the one below by mistake. You just want to make sure you have no dupes.

<Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\WebApplications\Microsoft.WebApplication.targets" />