diff --git a/Iyzipay.Samples/Sample.cs b/Iyzipay.Samples/Sample.cs
index 56168f4..38d6053 100644
--- a/Iyzipay.Samples/Sample.cs
+++ b/Iyzipay.Samples/Sample.cs
@@ -15,8 +15,8 @@ public class Sample
         public void Initialize()
         {
             options = new Options();
-            options.ApiKey = "your api key";
-            options.SecretKey = "your secret key";
+            options.ApiKey = "sandbox-X8Qfwvvb16pe2prgfeX857cwiD4bkfAf";
+            options.SecretKey = "sandbox-qaIiLIxhjMgx3LSKIVvp6j17NunHOFtD";
             options.BaseUrl = "https://sandbox-api.iyzipay.com";
         }
 
diff --git a/Iyzipay/IyzipayResourceV2.cs b/Iyzipay/IyzipayResourceV2.cs
index e2d0e73..065b4a3 100644
--- a/Iyzipay/IyzipayResourceV2.cs
+++ b/Iyzipay/IyzipayResourceV2.cs
@@ -4,6 +4,8 @@
 using System.Linq;
 using System.Net.Http;
 using System.Net.Http.Headers;
+using Newtonsoft.Json.Serialization;
+using Newtonsoft.Json;
 
 namespace Iyzipay
 {
@@ -69,8 +71,11 @@ private static String PrepareAuthorizationStringWithRequestBody(BaseRequestV2 re
         {
             String randomKey = GenerateRandomKey();
             String uriPath = FindUriPath(url);
-
-            String payload = request != null ? uriPath + JsonBuilder.SerializeObjectToPrettyJson(request) : uriPath;
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            String payload = request != null ? uriPath + JsonConvert.SerializeObject(request, settings) : uriPath; 
             String dataToEncrypt = randomKey + payload;
             String hash = HashGeneratorV2.GenerateHash(options.ApiKey, options.SecretKey, randomKey, dataToEncrypt); 
             return IYZIWS_V2_HEADER_NAME + hash;
diff --git a/Iyzipay/RestHttpClientV2.cs b/Iyzipay/RestHttpClientV2.cs
index b8c9e82..921b624 100644
--- a/Iyzipay/RestHttpClientV2.cs
+++ b/Iyzipay/RestHttpClientV2.cs
@@ -6,6 +6,8 @@
 using System.Net.Http.Headers;
 using System.Linq;
 using System.Threading.Tasks;
+using Newtonsoft.Json.Serialization;
+using System.Text;
 
 namespace Iyzipay
 {
@@ -45,14 +47,19 @@ public T Get<T>(String url, Dictionary<string, string> headers) where T : Iyzipa
 
 		public T Post<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Post,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Post,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
+            foreach (var header in headers)
 			{
 				requestMessage.Headers.Add(header.Key, header.Value);
 			}
@@ -64,14 +71,20 @@ public T Post<T>(String url, Dictionary<string, string> headers, BaseRequestV2 r
 		}
 		public async Task<T> PostAsync<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Post,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            string jsonContent = content.ReadAsStringAsync().Result;
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Post,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
+            foreach (var header in headers)
 			{
 				requestMessage.Headers.Add(header.Key, header.Value);
 			}
@@ -85,19 +98,24 @@ public async Task<T> PostAsync<T>(String url, Dictionary<string, string> headers
 
 		public T Put<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Put,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Put,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
-			{
-				requestMessage.Headers.Add(header.Key, header.Value);
-			}
+            foreach (var header in headers)
+            {
+                requestMessage.Headers.Add(header.Key, header.Value);
+            }
 
-			HttpResponseMessage httpResponseMessage = HttpClient.SendAsync(requestMessage).Result;
+            HttpResponseMessage httpResponseMessage = HttpClient.SendAsync(requestMessage).Result;
 			var response = JsonConvert.DeserializeObject<T>(httpResponseMessage.Content.ReadAsStringAsync().Result);
 			response.AppendWithHttpResponseHeaders(httpResponseMessage);
 			return response;
@@ -105,19 +123,24 @@ public T Put<T>(String url, Dictionary<string, string> headers, BaseRequestV2 re
 
 		public async Task<T> PutAsync<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Put,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Put,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
-			{
-				requestMessage.Headers.Add(header.Key, header.Value);
-			}
+            foreach (var header in headers)
+            {
+                requestMessage.Headers.Add(header.Key, header.Value);
+            }
 
-			HttpResponseMessage httpResponseMessage = HttpClient.SendAsync(requestMessage).Result;
+            HttpResponseMessage httpResponseMessage = HttpClient.SendAsync(requestMessage).Result;
 			var readAsString = await httpResponseMessage.Content.ReadAsStringAsync();
 			var response = JsonConvert.DeserializeObject<T>(readAsString);
 			response.AppendWithHttpResponseHeaders(httpResponseMessage);
@@ -127,11 +150,16 @@ public async Task<T> PutAsync<T>(String url, Dictionary<string, string> headers,
 
 		public T Patch<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
         {
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
             HttpRequestMessage requestMessage = new HttpRequestMessage
             {
-                Method = HttpMethod.Put,//todo: [EY] Patch olarak değiştirilmeli fakat kütüphane güncellenmesi gerekiyor.
+                Method = HttpMethod.Put,
                 RequestUri = new Uri(url),
-                Content = JsonBuilder.ToJsonString(request)
+                Content = content
             };
 
             foreach (var header in headers)
@@ -147,14 +175,19 @@ public T Patch<T>(String url, Dictionary<string, string> headers, BaseRequestV2
 
 		public T Delete<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Delete,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Delete,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
+            foreach (var header in headers)
 			{
 				requestMessage.Headers.Add(header.Key, header.Value);
 			}
@@ -167,14 +200,19 @@ public T Delete<T>(String url, Dictionary<string, string> headers, BaseRequestV2
 
 		public async Task<T> DeleteAsync<T>(String url, Dictionary<string, string> headers, BaseRequestV2 request) where T : IyzipayResourceV2
 		{
-			HttpRequestMessage requestMessage = new HttpRequestMessage
-			{
-				Method = HttpMethod.Delete,
-				RequestUri = new Uri(url),
-				Content = JsonBuilder.ToJsonString(request)
-			};
+            var settings = new JsonSerializerSettings
+            {
+                ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            };
+            var content = new StringContent(JsonConvert.SerializeObject(request, settings), Encoding.UTF8, "application/json");
+            HttpRequestMessage requestMessage = new HttpRequestMessage
+            {
+                Method = HttpMethod.Delete,
+                RequestUri = new Uri(url),
+                Content = content
+            };
 
-			foreach (var header in headers)
+            foreach (var header in headers)
 			{
 				requestMessage.Headers.Add(header.Key, header.Value);
 			}