C# – Duplicate ‘AssemblyVersion’ attribute

Problem

You’re trying to add the AssemblyVersion attribute to your project, like this (or perhaps you’re trying to auto-increment the version):

using System.Reflection;

[assembly: AssemblyVersion("1.0.0.0")]
[assembly: AssemblyFileVersion("1.0.0.0")]

Code language: C# (cs)

And you get the following compiler errors:

Error CS0579 Duplicate ‘AssemblyVersion’ attribute

Error CS0579 Duplicate ‘AssemblyFileVersion’ attribute

But you don’t see these attributes anywhere else in your project.

Solution

The problem is Visual Studio auto-generates the assembly info by default.

To turn this off, put the following in your .csproj file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>
  <PropertyGroup>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
  </PropertyGroup>
</Project>

Code language: HTML, XML (xml)

Where is the auto-generated assembly info?

My assembly is called DupeAssemblyVersion and I’m targeting .NET Core 3.1. So the auto-generated assembly info file is here: \obj\Debug\netcoreapp3.1\DupeAssemblyVersion.AssemblyInfo.cs.

Here’s what this file looks like:

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//     Runtime Version:4.0.30319.42000
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System;
using System.Reflection;

[assembly: System.Reflection.AssemblyCompanyAttribute("DupeAssemblyVersion")]
[assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
[assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0")]
[assembly: System.Reflection.AssemblyProductAttribute("DupeAssemblyVersion")]
[assembly: System.Reflection.AssemblyTitleAttribute("DupeAssemblyVersion")]
[assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]

// Generated by the MSBuild WriteCodeFragment class.
Code language: C# (cs)