Workflow contains an invalid custom activity.

Hi,

Below is my plain custom activity code.

using

System;

using

System.Collections.Generic;

using

System.Linq;

using

System.Text;

using

System.Activities;

using

System.Threading.Tasks;

using

Microsoft.Xrm.Sdk;

using

Microsoft.Xrm.Sdk.Workflow;

namespace

ActivityLibrary1

{

publicclassAudit :

CodeActivity

{

protectedoverridevoid Execute(CodeActivityContext

context)

{

//Create the IWorkflowContext and the

//IOrganizationService for communication with CRM

IWorkflowContext

workflowContext =

context.GetExtension<

IWorkflowContext

>();

IOrganizationServiceFactory

serviceFactory =

context.GetExtension<

IOrganizationServiceFactory

>();

IOrganizationService

service =

serviceFactory.CreateOrganizationService(workflowContext.UserId);

//Retrieve data from InputParameter

}

}

}

I am able to register the assembly and plugin uisng plugin registration tool, but when i am trying to add the custom activity to a process/workflow i m getting the below error.

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Workflow contains an invalid custom activity.Detail:
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
  <ErrorCode>-2147200968</ErrorCode>
  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
  <Message></Message>
  <Timestamp>2013-05-09T12:05:19.6794822Z</Timestamp>
  <InnerFault i:nil="true" />
  <TraceText i:nil="true" />
</OrganizationServiceFault>

Any help appreciated? Thank you.