Cloning record entites and the sub grids associated with it

Hello All,

Is there any efficient way to clone a custom entity record and it's associated subgrid records?

Which is preferable workflow/plugin?

I have used with CRM Online  EntityExtensions.Clone in a custom workflow but there was an error stating that

Plugin Trace:

Error Message:

Unhandled Exception: Microsoft.Crm.CrmException: Unexpected exception from plug-in (Execute): Workflows.Copy_Proposal: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Xrm.Client, Version=5.0.9689.2166, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
   at Microsoft.Crm.Sandbox.SandboxCodeUnit.Execute(IExecutionContext context)
   at Microsoft.Crm.Workflow.Services.ProxyCustomActivity.Execute(CodeActivityContext executionContext)