Loading Workflow dll as workflowservice

Question

I have workflow service xamlx that has recieve reply activities

//Current Setup
string fullPath1 = @"C:\Projects\Learning\Workflows\Approval1.xamlx";
WorkflowService service1 = XamlServices.Load(fullPath1) as WorkflowService;
WorkflowServiceHost host1 = new WorkflowServiceHost(service1);

CompileWorkflow(service1);

host1.Open();


static void CompileWorkflow(WorkflowService workflowService)
{
TextExpressionCompilerSettings settings = new TextExpressionCompilerSettings
{
.........}}  

// Would like to load dll instead of xamlx

string fullPath1 = @"C:\Projects\Learning\Workflows\bin\Approval1.dll"; // Not XAMLX
WorkflowService service1 = LoadWorkflowService(fullPath1);
WorkflowServiceHost host1 = new WorkflowServiceHost(service1);

host1.Open();

// Any ideas how to implement LoadWorkflowService()?