Here is the exception I got when retrieving a list of records from CRM:
A proxy type with the name account has been defined by another assembly. Current type: Plugins.Sdk.Account, Plugins, Version=18.104.22.168, Culture=neutral, PublicKeyToken=0b5679ac811dc738, Existing type: CrmSdk.Account, PluginRegisterTool, Version=22.214.171.124, Culture=neutral, PublicKeyToken=nullIn this case I was retrieving a list of PluginAssembly records, but the same exception happens when I try to retrieve ANY kind of entity. Also note that "Plugins.Sdk.Account, Plugins" is a type in the plug-in assembly that I'm trying to register, and "CrmSdk.Account, PluginRegistrationTool" is the type in the application that's actually doing the registration.
Parameter name: account
A look at the stack trace also gives us a hint about what's really happening here:
Server stack trace:
at Microsoft.Xrm.Sdk.AppDomainBasedKnownProxyTypesProvider.AddTypeMapping(Assembly assembly, Type type, String proxyName)
at Microsoft.Xrm.Sdk.KnownProxyTypesProvider.LoadKnownTypes(Assembly assembly)
at Microsoft.Xrm.Sdk.KnownProxyTypesProvider.RegisterAssembly(Assembly assembly)
So what's really happening here?