Merge pull request #235 from IsmailHassani/master

Fixed issue #233

Test/Flurl.Test/Http/DefaultUrlEncodedSerializerTests.cs

@@ -0,0 +1,55 @@
+using Flurl.Http.Configuration;
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Flurl.Test.Http
+{
+    [TestFixture, Parallelizable]
+    public class DefaultUrlEncodedSerializerTests
+    {
+        public class Grant
+        {
+            public string grant_type { get; set; }
+            public string username { get; set; }
+            public string password { get; set; }
+            public string refresh_token { get; set; }
+            public string client_id { get; set; }
+            public string client_secret { get; set; }
+            public string scope { get; set; }
+        }
+
+        public class Grant_Types
+        {
+            public const string password = "password";
+            public const string refresh_token = "refresh_token";
+            public const string client_credentials = "client_credentials";
+        }
+
+        public class Grant_Scopes
+        {
+            public const string password = "openid offline_access";
+            public const string client_credentials = "openid";
+        }
+
+        [Test]
+        public void can_serialize_with_grant_class()
+        {
+            var serializer = new DefaultUrlEncodedSerializer();
+            var result = serializer.Serialize(new Grant
+            {
+                grant_type = Grant_Types.password,
+                username = "user",
+                password = "password",
+                client_id = "Client_Id",
+                client_secret = "Client_Secret",
+                scope = Grant_Scopes.password
+            });
+
+            Assert.AreEqual("grant_type=password&username=user&password=password&client_id=Client_Id&client_secret=Client_Secret&scope=openid+offline_access", result.ToString());
+        }
+    }
+}

src/Flurl.Http/Configuration/DefaultUrlEncodedSerializer.cs

@@ -19,9 +19,13 @@ namespace Flurl.Http.Configuration
 				return null;
 
 			var qp = new QueryParamCollection();
-			foreach (var kv in obj.ToKeyValuePairs())
-				qp[kv.Key] = new QueryParameter(kv.Key, kv.Value);
-			return qp.ToString(true);
+            foreach (var kv in obj.ToKeyValuePairs())
+            {
+                // if value is null, the serializer shouldn't add this key-value pair.
+                if (kv.Value == null) continue;
+                qp[kv.Key] = new QueryParameter(kv.Key, kv.Value);
+            }
+            return qp.ToString(true);
 		}
 
 		/// <summary>