Duplicate AssemblyVersion Attribute

Question

I have a project that generates following error on compilation:

error CS0579: Duplicate \'AssemblyVersion\' attribute

I have che

Answer 1

Starting from Visual Studio 2017 another solution to keep using the AssemblyInfo.cs file is to turn off automatic assembly info generation like this:

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

I personally find it very useful for projects which need to support both .NET Framework and .NET Standard.

Answer 2

My error occurred because, somehow, there was an obj folder created inside my controllers folder. Just do a search in your application for a line inside your Assemblyinfo.cs. There may be a duplicate somewhere.

Answer 3

There must be already a AssemblyInfo.cs file in the project here:

To solve: - Delete any one AssemblyInfo.cs

Answer 4

I came across the same when tried add GitVersion tool to update my version in AssemblyInfo.cs. Use VS2017 and .NET Core project. So I just mixed both worlds. My AssemblyInfo.cs contains only version info that was generated by GitVersion tool, my csproj contains remaingin things. Please note I don't use <GenerateAssemblyInfo>false</GenerateAssemblyInfo> I use attributes related to version only (see below). More details here AssemblyInfo properties.

AssemblyInfo.cs

[assembly: AssemblyVersion("0.2.1.0")]
[assembly: AssemblyFileVersion("0.2.1.0")]
[assembly: AssemblyInformationalVersion("0.2.1+13.Branch.master.Sha.119c35af0f529e92e0f75a5e6d8373912d457818")]

my.csproj contains all related to other assemblyu attributes:

<PropertyGroup>
...
<Company>SOME Company </Company>
<Authors>Some Authors</Authors>
<Product>SOME Product</Product>
...
<GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
<GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute><GenerateAssemblyInformationalVersionAttribute>false</GenerateAssemblyInformationalVersionAttribute>

Answer 5

obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(15,12): error CS0579: Duplicate 'System.Reflection.AssemblyConfigurationAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]
obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(16,12): error CS0579: Duplicate 'System.Reflection.AssemblyFileVersionAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]
obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(17,12): error CS0579: Duplicate 'System.Reflection.AssemblyInformationalVersionAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]
obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(18,12): error CS0579: Duplicate 'System.Reflection.AssemblyProductAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]
obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(19,12): error CS0579: Duplicate 'System.Reflection.AssemblyTitleAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]
obj\Debug\netstandard2.0\PacktLibrary.AssemblyInfo.cs(20,12): error CS0579: Duplicate 'System.Reflection.AssemblyVersionAttribute' attribute [c:\Users\John_Tosh1\Documents\C#8.0and.NetCore3.0\Code\Chapter05\PacktLibrary\PacktLibrary.csproj]

I believe my Library folder was corrupted by an inadvertent creation of another class library.I deleted the library an all associated file but the problem persisted. I found a workaround by deleting ALL bin and obj folders in the directory. The build was ok previously but found a subfolder that had the same assemblyinfo.cs file.

Answer 6

If you're having this problem in a Build Pipeline on Azure DevOps, try putting the Build Action as "Content" and Copy to Output Directory equal to "Copy if newer" in the AssembyInfo.cs file properties.