[WIP] Update service invocation examples

daprdocs/content/en/developing-applications/building-blocks/service-invocation/howto-invoke-discover-services.md

@@ -199,11 +199,14 @@ namespace EventService
                System.Threading.Thread.Sleep(5000);
                Random random = new Random();
                int orderId = random.Next(1,1000);
-               using var client = new DaprClientBuilder().Build();
 
                //Using Dapr SDK to invoke a method
-               var result = client.CreateInvokeMethodRequest(HttpMethod.Get, "checkout", "checkout/" + orderId);
-               await client.InvokeMethodAsync(result);
+               var order = new Order("1");
+               var orderJson = JsonSerializer.Serialize<Order>(order);
+               var content = new StringContent(orderJson, Encoding.UTF8, "application/json");
+
+               var httpClient = DaprClient.CreateInvokeHttpClient();
+               await httpClient.PostAsJsonAsync($"http://orderprocessor/orders", content);               
                Console.WriteLine("Order requested: " + orderId);
                Console.WriteLine("Result: " + result);
    	    }