A plugin with 'plugin.name' system name is already defined

rajupaladiya wrote:
Can you explain what you mean by release and build output folder? In my .csproj file (as well as the included plugins .csproj file) I see an <OutputPath> tag and that is it.

In the Build dialog, there is a Configuration drop down in the upper left corner.

New York wrote:
I verified the output path is set correctly.

New York wrote:
Where do I check the dependencies?

New York wrote:
Thank you. My configuration is Active (Debug), which seems to match the included the plugins. Is this the correct configuration to use?

I finally (mostly) solved this.  I started with the suggested .csproj file in the documentation and found several issues and made the following changes.
From:

<CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>

To:

<CopyLocalLockFileAssemblies>false</CopyLocalLockFileAssemblies>

From:

<ItemGroup>
        <ProjectReference Include="..\..\Presentation\Nop.Web.Framework\Nop.Web.Framework.csproj" />
    </ItemGroup>

To:

<ItemGroup>
    <ProjectReference Include="..\..\Presentation\Nop.Web.Framework\Nop.Web.Framework.csproj" />
    <ProjectReference Include="..\..\Presentation\Nop.Web\Nop.Web.csproj" />
    <ClearPluginAssemblies Include="$(MSBuildProjectDirectory)\..\..\Build\ClearPluginAssemblies.proj" />
  </ItemGroup>

From:

<MSBuild Projects="@(ClearPluginAssemblies)" Properties="PluginPath=$(MSBuildProjectDirectory)\ $(OutDir)" Targets="NopClear" />

To:

<MSBuild Projects="@(ClearPluginAssemblies)" Properties="PluginPath=$(MSBuildProjectDirectory)\$(OutDir)" Targets="NopClear" />

The last change is subtle; I removed the space between "\" and "$".

These changes did solve everything. I was still left with the following folders in the output directory, which I manually deleted.

App_Data
Areas
Plugins
Properties
Themes

There is an active thread discussing this last issue:

https://www.nopcommerce.com/boards/topic/73910/plugin-output-directory-pulling-in-nopweb-directories#

In Visual studio, Go to Each plugin project explorer, and navigate to
Dependencies\Projects
  if you see the node "Nop.Web" under that plugin, then click it, and go to its properties:
  and set property "Copy Local" = "No"
Do this for all plugin projects.

See picture:

https://imgur.com/a/s4xNjJU

I downloaded the project and try to run and get this error. How is this possible when I haven't made any changes to the project?

I added this and now it works. Not sure why this isn't included in the release I just downloaded today..
https://github.com/nopSolutions/nopCommerce/commit/7b9f8f0fb6178c40b92167ebdaa049a21a47b1ee

arjunshetty2020 wrote:

worked for me

This answer fixed it for me in Visual Studio 2019: https://www.nopcommerce.com/en/boards/topic/72937/help-systemexception-a-plugin-with-sevenspikesnoppluginscategoriesheadermenu-system-name-is-already-/page/2#249810

Here is the link to the fix in that answer: https://github.com/nopSolutions/nopCommerce/commit/7b9f8f0fb6178c40b92167ebdaa049a21a47b1ee