error CS1703 on Unity 2018.3.9f1

[Alby90]

When i import the plugin folder into my assets Folder i've got 4 instances of this error:

error CS1703: Multiple assemblies with equivalent identity have been imported: 'C:------------\Assets\Plugins\System.Data.dll' and 'C:\Program Files\Unity\Hub\Editor\2018.3.9f1\Editor\Data\MonoBleedingEdge\lib\mono\4.7.1-api\System.Data.dll'. Remove one of the duplicate references.

Unity Version 2018.3.9f1 but i found this problem in 2018.3.7f1 as well...

[rizasif]

Seems like somehow your system variables are hindering the sqlite compilation. Try checking your environment.

[KevinFournier]

I had the same error, I deleted (as the error message suggests) the System.Data.dll and its meta file from the plugin. It work fine now.

This error appear because the dll is in your Plugins folder and in C:\Program Files\Unity\Hub\Editor\2018.3.9f1\Editor\Data\MonoBleedingEdge\lib\mono\4.7.1-api\System.Data.dll. As it is present in both with the same name, Unity doesn't know wich one to use.

Note : I didn't do much with the plugin, just few basic connections / writting / reading, so I do not know if it can trigger error afterwards or if one of the dll is older than the other. Nonetheless, I rather delete the one from the plugin ; if Unity use the other internally, it could be a bad idea to delete it.

[ssshake]

I can confirm this issue in unity 2019.x.x

Is it possible that this is built into unity now or something like that? Deleting the system.data.dll file also solved the problem for me

[higamy]

I got the same error in Unity 2020.x.x and as per the others, deleting the duplicate file from the plugins folder removed the error message.
I don't know if this will compromise other functionality later though so it would be good to know if this version of the file is different to the one already in my Unity installation and if there are any known problems with deleting it.