My class (THPMSBridge.RealtimeNetworkState) implements a interface "INetworkState" in another assembly, and this causes a exception during runtime:

A first chance exception of type 'System.TypeLoadException' occurred in
System.Windows.Forms.dll

Additional information: Type 'THPMSBridge.RealtimeNetworkState' from assembly
'THPMSBridge, Version=1.0.50721.0, Culture=neutral, PublicKeyToken=null' is
attempting to implement an inaccessible interface.

Could anyone explain what this exception is? How to fix it?

Thanks!