Attribute 'TargetFrameworkAttribute' cannot be applied multiple times.

[Pranay N]

Hello Govert, 

I'm using Visual Studio 2022 with Excel DNA 1.8.0 and I get the following error when trying to build my addin:

Attribute 'TargetFrameworkAttribute' cannot be applied multiple times.

When I click on the error message, it takes me to a file created in the Debug folder

"C:\Users..\Debug\.NETFramework,Version=v4.7.2.AssemblyAttributes.vb"

The file contains the following code:

' <autogenerated/>
            Option Strict Off
            Option Explicit On

            Imports System
            Imports System.Reflection
            <Assembly: Global.System.Runtime.Versioning.TargetFrameworkAttribute(".NETFramework,Version=v4.7.2", FrameworkDisplayName:=".NET Framework 4.7.2")>

[Govert van Drimmelen]

Your project might have an assembly properties file that sets TargetFramework too, clashing with the generated file you show.

This would happen if your converting from an old-style project file to a new .vbproj file.

For this case, remove the extra file in your project.

 

You can also prevent the build from generating this attribute at build time with this project property

    <GenerateTargetFrameworkAttribute>false</GenerateTargetFrameworkAttribute>

 

-Govert

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[Pranay N]

Thank you Govert for quick response. However, I have to admit I'm lost here.  I do not have any such file setting assembly properties in my project. 

Here is my packages.config file content:

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="ExcelDna.AddIn" version="1.8.0" targetFramework="net472" />
  <package id="ExcelDna.Integration" version="1.8.0" targetFramework="net472" />
  <package id="ExcelDna.IntelliSense" version="1.8.0" targetFramework="net472" />
  <package id="ExcelDna.Interop" version="15.0.1" targetFramework="net472" />
  <package id="ExcelDna.Registration" version="1.8.0" targetFramework="net472" />
  <package id="ExcelDna.XmlSchemas" version="1.0.0" targetFramework="net472" />
  <package id="ExcelDnaDoc" version="1.8.0" targetFramework="net472" />
  <package id="Microsoft.CSharp" version="4.7.0" targetFramework="net472" />
</packages>

And here is my MyAddin-AddIn.dna file content:

<?xml version="1.0" encoding="utf-8"?>
<DnaLibrary Name="MyAdd-In" RuntimeVersion="v4.0" xmlns="http://schemas.excel-dna.net/addin/2020/07/dnalibrary">
  <ExternalLibrary Path="MyAddin.dll" ExplicitExports="true" LoadFromBytes="true" Pack="true" IncludePdb="false" ComServer="true"/>

<Reference Path="ExcelDna.IntelliSense.dll" Pack="true" />
<Reference Path="ExcelDna.Documentation.dll" Pack="true" />

<!--
       The RuntimeVersion attribute above allows the following settings:
       * RuntimeVersion="v4.0" - for .NET Framework 4.5 or higher
       * v6.0, v7.0, v8.0 etc. for .NET

       You can have IntelliSense (autocomplete) and validation for this file.
       See https://github.com/Excel-DNA/ExcelDna/tree/master/Distribution/XmlSchemas/

       Additional referenced assemblies can be specified by adding 'Reference' tags.
       These libraries will not be examined and registered with Excel as add-in libraries,
       but will be packed into the -packed.xll file and loaded at runtime as needed.
       For example:

       <Reference Path="Another.Library.dll" Pack="true" />

       Excel-DNA also allows the XML for ribbon UI extensions to be specified in the .dna file.
       See the main Excel-DNA site at https://excel-dna.net for downloads of the full distribution.
  -->
</DnaLibrary>

[Govert van Drimmelen]

In Visual Studio in the Solution Explorer, if you click the “Show All Files” button, you might see files like “AssemblyInfo.vb”.

Check whether you have a TargetFramework entry in there.

 

To view this discussion visit https://groups.google.com/d/msgid/exceldna/ddfcd302-5e78-4899-865d-fab5db4258c3n%40googlegroups.com.

[Pranay N]

There is all I have in AssemblyInfo.vb:

Imports System
Imports System.Reflection
Imports System.Runtime.InteropServices

' General Information about an assembly is controlled through the following
' set of attributes. Change these attribute values to modify the information
' associated with an assembly.

' Review the values of the assembly attributes

<Assembly: AssemblyTitle("MyAddin")>
<Assembly: AssemblyDescription("xxx")>
<Assembly: AssemblyCompany("xxx")>
<Assembly: AssemblyProduct("xxx")>
<Assembly: AssemblyCopyright("Copyright ©  2025")>
<Assembly: AssemblyTrademark("")>

<Assembly: ComVisible(False)>

'The following GUID is for the ID of the typelib if this project is exposed to COM
<Assembly: Guid("6e7ae120-a28b-44ec-bf94-0fe36b0ef14d")>

' Version information for an assembly consists of the following four values:
'
'      Major Version
'      Minor Version
'      Build Number
'      Revision
'

<Assembly: AssemblyVersion("2.6.9.0")>
<Assembly: AssemblyFileVersion("1.0.0.0")>

[Govert van Drimmelen]

When I build, I get the same file in the obj\Debug folder, but no error.

So I think you might have this attribute somewhere in a file that your project incorporates.

Maybe under the Properties folder.

 

If you can make a small project that has this problem and you can post on GitHub or somewhere, I’d be happy to have a look.

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[Pranay N]

Thank you again for all the help, Govert.

I will keep trying and post the solution if and when I find it.  

A bit more background here:

I've been using your add-in for over 10 years and I have not upgraded to latest versions in recent years.  The update on my add in was using 1.6 in 2023.  I ran into several issues when attempting to upgrade to 1.8.  Therefore, I created a brand-new class library project, installed all nuget packages and moved all my code into this new file.  All the files I moved contains background program logic and should have no refences to TargetFramework.  I will have to go through them one by one to get to the bottom of the issue.  Thank you again for all your contributions to this amazing project.