Add to MySql.Data error

I tried to join MySql.Data.dll in assets to enable Unity can connect database
But when MySql.Data.dll added assets, the following error

How can I fix? Seems to have many similar problems, but most did not solve my problem

Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module can not be loaded.

at (wrapper managed-to-native) System.Reflection.Assembly: GetTypes (bool)

at System.Reflection.Assembly.GetTypes () [0x00000] in : 0

at Mono.CSharp.RootNamespace.ComputeNamespaces (System.Reflection.Assembly assembly, System.Type extensionType) [0x00000] in : 0

at Mono.CSharp.RootNamespace.ComputeNamespace (Mono.CSharp.CompilerContext ctx, System.Type extensionType) [0x00000] in : 0

at Mono.CSharp.GlobalRootNamespace.ComputeNamespaces (Mono.CSharp.CompilerContext ctx) [0x00000] in : 0

at Mono.CSharp.Driver.LoadReferences () [0x00000] in : 0

at Mono.CSharp.Driver.Compile () [0x00000] in : 0

at Mono.CSharp.Driver.Main (System.String args) [0x00000] in : 0



same problem with unity5.4

Upgrade or you can clear it and ignore it, or add a different namespace.