update asp.net-mssql sample

Signed-off-by: Anca Iordache <anca.iordache@docker.com>

samples/aspnet-mssql/app/aspnetapp/Models/ErrorViewModel.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace aspnetapp.Models
+{
+    public class ErrorViewModel
+    {
+        public string RequestId { get; set; }
+
+        public bool ShowRequestId => !string.IsNullOrEmpty(RequestId);
+    }
+}