Plugin's Starter Execution Method

Have found excellent method at David Fronk blog Starter Execution Method and slightly update it in to separate method.

// based on Starter Execution Method

/// 

/// Return the opportunity id
/// 
/// Plugin context/// opportunityid
public string GetEntityId(IPluginExecutionContext context)
{
 string opportunityid = "";
 DynamicEntity opportunityClose = null;

 switch (context.MessageName)
 {
  case "Create":
   if (context.OutputParameters.Properties.Contains("id"))
   {
    opportunityid = context.OutputParameters.Properties["id"].ToString();
   }
   break;
  case "Update":
   if (context.InputParameters.Properties.Contains(ParameterName.Target) && context.InputParameters.Properties[ParameterName.Target] is DynamicEntity)
   {
    DynamicEntity entity = (DynamicEntity)context.InputParameters.Properties[ParameterName.Target];
    opportunityid = ((Key)entity.Properties["opportunityid"]).Value.ToString();
   }
   break;
  case "SetState":
   if (context.InputParameters.Properties.Contains("EntityMoniker"))
   {
    if (context.InputParameters.Properties.Contains("State"))
    {
     Moniker entityMoniker = (Moniker)context.InputParameters.Properties[ParameterName.EntityMoniker];
     opportunityid = entityMoniker.Id.ToString();
    }
   }
   break;
  case "SetStateDynamicEntity":
   if (context.InputParameters.Properties.Contains("EntityMoniker"))
   {
    if (context.InputParameters.Properties.Contains("State"))
    {
     Moniker entityMoniker = (Moniker)context.InputParameters.Properties[ParameterName.EntityMoniker];
     opportunityid = entityMoniker.Id.ToString();
    }
   }
   break;
  case "Win":
   opportunityClose = (DynamicEntity)context.InputParameters["OpportunityClose"];
   Lookup WonLook = (Lookup)opportunityClose.Properties["opportunityid"];
   opportunityid = WonLook.Value.ToString();
   break;
  case "Lose":
   opportunityClose = (DynamicEntity)context.InputParameters["OpportunityClose"];
   Lookup LoseLook = (Lookup)opportunityClose.Properties["opportunityid"];
   opportunityid = LoseLook.Value.ToString();
   break;
  case "Assign":
   if (context.InputParameters.Properties.Contains("Assignee") && context.InputParameters.Properties["Assignee"] is SecurityPrincipal)
   {
    Moniker assignEntity = (Moniker)context.InputParameters.Properties["Target"];
    opportunityid = assignEntity.Id.ToString();
   }
   break;
  case "Delete":
   if (context.InputParameters.Properties.Contains("Target"))
   {
    Moniker entityMoniker = null;
    entityMoniker = (Moniker)context.InputParameters.Properties[ParameterName.Target];
    opportunityid = entityMoniker.Id.ToString();
   }
   break;
 }
 return opportunityid;
}