CRM2013. C#. Activate, Update and Deactivate case.

Hi.

Have a plugin which starts on Email PreCreate. Plugin must activate the email regarding Case, update some field in the Case and deactivate the Case back.

Here is the plugin code:

IPluginExecutionContext context = localContext.PluginExecutionContext;
IOrganizationService service = localContext.OrganizationService;

if (context.InputParameters.Contains("Target") && context.InputParameters["Target"] is Entity)
{
    Entity entity = (Entity)context.InputParameters["Target"];

    try
    {
        var regardingCaseId = ((EntityReference)entity.Attributes["regardingobjectid"]).Id;
        Entity regardingCase = service.Retrieve("incident", regardingCaseId, new ColumnSet(true));
        int status = ((OptionSetValue)regardingCase.Attributes["statuscode"]).Value;
        if (status == 5)
        {
            // Activate case
            SetStateRequest setStateRequest = new SetStateRequest()
            {
                EntityMoniker = new EntityReference
                {
                    Id = regardingCaseId,
                    LogicalName = "incident",
                },
                State = new OptionSetValue(0),
                Status = new OptionSetValue(1)
            };
            service.Execute(setStateRequest);
            // UPDATE Add some changes
            regardingCase["description"] = "xxxxx";
            service.Update(regardingCase);

            // Deactivate case
            setStateRequest = new SetStateRequest()
            {
                EntityMoniker = new EntityReference
                {
                    Id = regardingCaseId,
                    LogicalName = "incident",
                },
                State = new OptionSetValue(1),
                Status = new OptionSetValue(5)
            };
            service.Execute(setStateRequest);
        }
    }
    catch
    {
        return;
    }
}

In result it throws error:

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: There is no active transaction. This error is usually caused by custom plug-ins that ignore errors from service calls and continue processing.Detail: <OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts"><ErrorCode>-2147220911</ErrorCode><ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" /><Message>There is no active transaction. This error is usually caused by custom plug-ins that ignore errors from service calls and continue processing.</Message><Timestamp>2014-07-09T10:25:31.5511394Z</Timestamp><InnerFault i:nil="true" /><TraceText i:nil="true" /></OrganizationServiceFault>

But plugin completes fine and activate the case if I remove Update step and Deactivate step.

Why it does not work with update and deactivate steps? And how to fix it?

Thanks!