.NET core 3.0 and MS Office Interop

Question

I am trying to use the recently-released .NET core with MS Office using the interop assemblies

I've got a minimal project file

<Project Sdk="Microsoft.NET.Sdk">    <PropertyGroup>     <OutputType>Exe</OutputType>     <TargetFramework>netcoreapp3.0</TargetFramework>   </PropertyGroup>    <ItemGroup>     <PackageReference Include="Microsoft.Office.Interop.Word">       <Version>15.0.4797.1003</Version>     </PackageReference>   </ItemGroup>  </Project> 

and this C# program

using System; using Microsoft.Office.Interop.Word; namespace ii {     class Program     {         static void Main(string[] args)         {             var app = new Application();             Console.WriteLine(app.Version);             app.Quit();         }     } } 

Unfortunately this fails with

Unhandled exception. System.IO.FileNotFoundException: Could not load file or assembly 'office, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'. The system cannot find the file specified. File name: 'office, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' 

When I added the package to the project I got this

warn : Package 'Microsoft.Office.Interop.Word 15.0.4797.1003' was restored using '.NETFramework,Version=v4.6.1, .NETFramework,Version=v4.6.2, .NETFramework,Version=v4.7, .NETFramework,Version=v4.7.1, .NETFramework,Version=v4.7.2, .NETFramework,Version=v4.8' instead of the project target framework '.NETCoreApp,Version=v3.0'. This package may not be fully compatible with your project. info : Package 'Microsoft.Office.Interop.Word' is compatible with all the specified frameworks in project  

implying 'compatible' but not 'fully compatible'

Is there a way to do this or must I use .NET Framework instead of Core?

I am using Windows 10, .NET core 3.0.100 and MS Office 365 (Word is version 16.0.11929.20298)

Answer 1

I had the same issue. I fixed it by opening the reference properties and setting both "Copy Local" and "Embed Interop Types" to "Yes".

Update: This actually does the same thing as adding these 2 lines to the COM reference in the .csproj file.

<COMReference Include="Microsoft.Office.Core">     ...     <EmbedInteropTypes>True</EmbedInteropTypes>     <Private>true</Private> </COMReference> 

The "Private" tag isn't mentioned in the accepted answers, but it prevents a lot of problems.

Answer 2

The solution to this is a bit quirky, but possible.

Create a new .NET Framework 4.X project. Add the relevant COM references to the project. Edit the .csproj of your .NET Core 3.0 project and add the generated references from the .NET Framework project to the <ItemGroup> tag.

It should look something similar to:

<ItemGroup>     <COMReference Include="Microsoft.Office.Core">       <Guid>{2DF8D04C-5BFA-101B-BDE5-00AA0044DE52}</Guid>       <VersionMajor>2</VersionMajor>       <VersionMinor>8</VersionMinor>       <Lcid>0</Lcid>       <WrapperTool>primary</WrapperTool>       <Isolated>False</Isolated>       <EmbedInteropTypes>True</EmbedInteropTypes>     </COMReference>  ... more references  </ItemGroup> 

Do not use the NuGet packages, they are not compatible with .NET Core.

Update:

You can now add the COM references straight from the IDE (since Visual Studio 2019 v16.6):