From 7a9d3dc187ccbfe48904f7962f92b524e7c84685 Mon Sep 17 00:00:00 2001
From: "jason.zhu" <jason.zhu@xero.com>
Date: Wed, 16 Jun 2021 15:19:43 +1000
Subject: [PATCH] Finished 'Attribute Routing with Optional Parameter'

---
 2_Routing.md | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/2_Routing.md b/2_Routing.md
index 86dfa3d..9a4fd62 100644
--- a/2_Routing.md
+++ b/2_Routing.md
@@ -293,8 +293,31 @@ Now `http://localhost:xxxx/students/2/courses` will be routed to `GetStudentCour
 * controller action method have `[Route]` attribute use Attribute Routing
 * controller action method without `[Route]` attribute uses Convention-based routing.
 
-## Attribute Routing in ASP.NET MVC
-
 ## Attribute Routing with Optional Parameter
 
+URI parameter can also be defined in attribute routing by adding **question mark ("?")** to router parameter within `{}`. We can also specify default value by **parameter = value** 
+
+e.g. optional URI Parameter `{studentName? }`
+
+```csharp
+        // Optional URI Parameter
+        // URL: /MVCTest/
+        // URL: /MVCTest/Pranaya
+        [Route("MVCTest/{studentName ?}")]
+        public ActionResult MVC(string studentName)
+        {
+            DoSth(studentName);
+            return View();
+        }
+        // Optional URI Parameter with default value
+        // URL: /WEBAPITest/
+        // URL: /WEBAPITest/Pranaya
+        [Route("WEBAPITest/{studentName = Pranaya}")]
+        public ActionResult WEBAPI(string studentName)
+        {
+            DoSth(studentName);
+            return View();
+        }
+```
+
 ## Route Prefix in Attribute Routing
\ No newline at end of file