TypeLoadException: Could not load type from assembly

I create a plugin and import the dll reference to my project. When execute it, it has the following error:

TypeLoadException: Could not load type ‘HOH_SQLite.HOH_SQLiteConnection’ from assembly ‘HOH_SQLite, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null’.

My library targets at .NET 2.0 ( also tried 3.5 but nothing helped ). Can anyone help? ;(

UPDATE

I wrote a rough program testing my dll, it also throws an error but more specific :
System.Data.SQLite not found

I suspect it is the cause of TypeLoadException, any ways that I can embed my System.Data.SQLite.dll into HOH_SQLite.dll?

You need all dependencies that aren’t already part of the Mono core / Unity engine inside your project. So have you copied the “System.Data.SQLite.dll” into your project? Unity does not rely on any external framework like .NET. Everything need to be inside the project itself.

Keep in mind that if you use assemblies which have native DLL dependencies you might not be able to use those at all depending on your target platform.

I got a similar problem.
TypeLoadException: Count not load type ‘System.data.Oledb.OledbConnection’ from assembly ‘System.Data, Version=2.0.0.0, Cultrue=neutral, PublicKeyToken=b77a5c561934e089’ .
Looking for help.