Merge pull request #264 from caioproiete/display-error-when-using-nug…

…et-packagereference

Display error message to user if project is using NuGet PackageReference

Package/ExcelDna.AddIn/build/ExcelDna.AddIn.targets

@@ -60,6 +60,14 @@
     <ExcelDnaPackRunMultithreaded Condition="'$(ExcelDnaPackRunMultithreaded)' == ''">true</ExcelDnaPackRunMultithreaded>
   </PropertyGroup>
 
+  <!--
+    Target that checks if the project is not compatible with Excel-DNA
+  -->
+  <Target Name="ExcelDnaCheckPackageProjectStyle" BeforeTargets="CoreCompile">
+    <Error Text="Excel-DNA is not compatible with projects that use NuGet `PackageReference`. Make sure you create a .NET Framework (Class Library) project and configure Visual Studio to use `packages.config`"
+           Condition=" '$(PackageReferenceCompatibleProjectStyle)' == 'true' OR '$(RestoreProjectStyle)' == 'ProjectJson' OR '$(NuGetProjectStyle)' == 'PackageReference' " />
+  </Target>
+
   <!--
     Configure debugger options (Path for EXCEL.EXE, add-in to open, etc).
   -->