// Refer http://msdn.microsoft.com/en-us/library/ms914670.aspx 
// for StateCode's (Status) and StatusCode's (Status Reason)
 
IOrganizationService service;
new_entity record; // a record of new_entity, can be any Entity
 
var setStateRequest = new SetStateRequest();
setStateRequest.EntityMoniker = new EntityReference(record.LogicalName, record.Id);
 
// State property corresponds to the StateCode of an Entity. Its' shown as the Status in CRM
setStateRequest.State = new OptionSetValue((int)new_entityState.Inactive);
 
// Status property corresponds to the StatusCode of an Entity. Its' shown as the StatusReason in CRM
// set this value to -1 to let the system automatically set the appropiate corresponding status value
setStateRequest.Status = new OptionSetValue(-1);
 
var response = (SetStateResponse)service.Execute(setStateRequest);