diff --git a/CryptoExchange.Net/Attributes/NullableAttributes.cs b/CryptoExchange.Net/Attributes/NullableAttributes.cs
index 11267ea..156ac83 100644
--- a/CryptoExchange.Net/Attributes/NullableAttributes.cs
+++ b/CryptoExchange.Net/Attributes/NullableAttributes.cs
@@ -1,4 +1,4 @@
-#if !NETSTANDARD2_1
+#if NETSTANDARD2_0
 namespace System.Diagnostics.CodeAnalysis
 {
     using System;
diff --git a/CryptoExchange.Net/Caching/MemoryCache.cs b/CryptoExchange.Net/Caching/MemoryCache.cs
index 35f93c2..143e07d 100644
--- a/CryptoExchange.Net/Caching/MemoryCache.cs
+++ b/CryptoExchange.Net/Caching/MemoryCache.cs
@@ -26,7 +26,7 @@ namespace CryptoExchange.Net.Caching
         /// <returns>Cached value if it was in cache</returns>
         public object? Get(string key, TimeSpan maxAge)
         {
-            _cache.TryGetValue(key, out CacheItem value);
+            _cache.TryGetValue(key, out CacheItem? value);
             if (value == null)
                 return null;
 
diff --git a/CryptoExchange.Net/Clients/BaseClient.cs b/CryptoExchange.Net/Clients/BaseClient.cs
index d0740c6..0916c31 100644
--- a/CryptoExchange.Net/Clients/BaseClient.cs
+++ b/CryptoExchange.Net/Clients/BaseClient.cs
@@ -15,7 +15,7 @@ namespace CryptoExchange.Net.Clients
         /// <summary>
         /// Version of the CryptoExchange.Net base library
         /// </summary>
-        public Version CryptoExchangeLibVersion { get; } = typeof(BaseClient).Assembly.GetName().Version;
+        public Version CryptoExchangeLibVersion { get; } = typeof(BaseClient).Assembly.GetName().Version!;
 
         /// <summary>
         /// Version of the client implementation
@@ -27,7 +27,7 @@ namespace CryptoExchange.Net.Clients
                lock(_versionLock)
                 {
                     if (_exchangeVersion == null)
-                        _exchangeVersion = GetType().Assembly.GetName().Version;
+                        _exchangeVersion = GetType().Assembly.GetName().Version!;
 
                     return _exchangeVersion;
                 }
diff --git a/CryptoExchange.Net/Clients/RestApiClient.cs b/CryptoExchange.Net/Clients/RestApiClient.cs
index 91e999a..ace6642 100644
--- a/CryptoExchange.Net/Clients/RestApiClient.cs
+++ b/CryptoExchange.Net/Clients/RestApiClient.cs
@@ -807,7 +807,7 @@ namespace CryptoExchange.Net.Clients
             if (parameterPosition == HttpMethodParameterPosition.InUri)
             {
                 foreach (var parameter in parameters)
-                    uri = uri.AddQueryParmeter(parameter.Key, parameter.Value.ToString());
+                    uri = uri.AddQueryParmeter(parameter.Key, parameter.Value.ToString()!);
             }
 
             var headers = new Dictionary<string, string>();
diff --git a/CryptoExchange.Net/Converters/JsonNet/ArrayConverter.cs b/CryptoExchange.Net/Converters/JsonNet/ArrayConverter.cs
index 6a286da..4a2180e 100644
--- a/CryptoExchange.Net/Converters/JsonNet/ArrayConverter.cs
+++ b/CryptoExchange.Net/Converters/JsonNet/ArrayConverter.cs
@@ -36,7 +36,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
 
             var result = Activator.CreateInstance(objectType);
             var arr = JArray.Load(reader);
-            return ParseObject(arr, result, objectType);
+            return ParseObject(arr, result!, objectType);
         }
 
         private static object ParseObject(JArray arr, object result, Type objectType)
@@ -58,25 +58,25 @@ namespace CryptoExchange.Net.Converters.JsonNet
                     var count = 0;
                     if (innerArray.Count == 0)
                     {
-                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { 0 });
+                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { 0 })!;
                         property.SetValue(result, arrayResult);
                     }
                     else if (innerArray[0].Type == JTokenType.Array)
                     {
-                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { innerArray.Count });
+                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { innerArray.Count })!;
                         foreach (var obj in innerArray)
                         {
                             var innerObj = Activator.CreateInstance(objType!);
-                            arrayResult[count] = ParseObject((JArray)obj, innerObj, objType!);
+                            arrayResult[count] = ParseObject((JArray)obj, innerObj!, objType!);
                             count++;
                         }
                         property.SetValue(result, arrayResult);
                     }
                     else
                     {
-                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { 1 });
+                        var arrayResult = (IList)Activator.CreateInstance(property.PropertyType, new [] { 1 })!;
                         var innerObj = Activator.CreateInstance(objType!);
-                        arrayResult[0] = ParseObject(innerArray, innerObj, objType!);
+                        arrayResult[0] = ParseObject(innerArray, innerObj!, objType!);
                         property.SetValue(result, arrayResult);
                     }
                     continue;
@@ -88,7 +88,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
                 object? value;
                 if (converterAttribute != null)
                 {
-                    value = arr[attribute.Index].ToObject(property.PropertyType, new JsonSerializer {Converters = {(JsonConverter) Activator.CreateInstance(converterAttribute.ConverterType)}});
+                    value = arr[attribute.Index].ToObject(property.PropertyType, new JsonSerializer {Converters = {(JsonConverter) Activator.CreateInstance(converterAttribute.ConverterType)!}});
                 }
                 else if (conversionAttribute != null)
                 {
@@ -120,7 +120,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
                     }
                     else if ((property.PropertyType == typeof(decimal)
                      || property.PropertyType == typeof(decimal?))
-                     && (value != null && value.ToString().IndexOf("e", StringComparison.OrdinalIgnoreCase) >= 0))
+                     && (value != null && value.ToString()!.IndexOf("e", StringComparison.OrdinalIgnoreCase) >= 0))
                     {
                         var v = value.ToString();
                         if (decimal.TryParse(v, NumberStyles.Float, CultureInfo.InvariantCulture, out var dec))
@@ -164,7 +164,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
                 last = arrayProp.Index;
                 var converterAttribute = GetCustomAttribute<JsonConverterAttribute>(prop);
                 if (converterAttribute != null)
-                    writer.WriteRawValue(JsonConvert.SerializeObject(prop.GetValue(value), (JsonConverter)Activator.CreateInstance(converterAttribute.ConverterType)));
+                    writer.WriteRawValue(JsonConvert.SerializeObject(prop.GetValue(value), (JsonConverter)Activator.CreateInstance(converterAttribute.ConverterType)!));
                 else if (!IsSimple(prop.PropertyType))
                     serializer.Serialize(writer, prop.GetValue(value));
                 else
@@ -187,9 +187,9 @@ namespace CryptoExchange.Net.Converters.JsonNet
         }
 
         private static T? GetCustomAttribute<T>(MemberInfo memberInfo) where T : Attribute =>
-            (T?)_attributeByMemberInfoAndTypeCache.GetOrAdd((memberInfo, typeof(T)), tuple => memberInfo.GetCustomAttribute(typeof(T)));
+            (T?)_attributeByMemberInfoAndTypeCache.GetOrAdd((memberInfo, typeof(T)), tuple => memberInfo.GetCustomAttribute(typeof(T))!);
 
         private static T? GetCustomAttribute<T>(Type type) where T : Attribute =>
-            (T?)_attributeByTypeAndTypeCache.GetOrAdd((type, typeof(T)), tuple => type.GetCustomAttribute(typeof(T)));
+            (T?)_attributeByTypeAndTypeCache.GetOrAdd((type, typeof(T)), tuple => type.GetCustomAttribute(typeof(T))!);
     }
 }
diff --git a/CryptoExchange.Net/Converters/JsonNet/BigDecimalConverter.cs b/CryptoExchange.Net/Converters/JsonNet/BigDecimalConverter.cs
index ad773b1..80777c1 100644
--- a/CryptoExchange.Net/Converters/JsonNet/BigDecimalConverter.cs
+++ b/CryptoExchange.Net/Converters/JsonNet/BigDecimalConverter.cs
@@ -27,7 +27,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
             {
                 try
                 {
-                    return decimal.Parse(reader.Value!.ToString(), NumberStyles.Float, CultureInfo.InvariantCulture);
+                    return decimal.Parse(reader.Value!.ToString()!, NumberStyles.Float, CultureInfo.InvariantCulture);
                 }
                 catch (OverflowException) 
                 {
@@ -40,7 +40,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
             {
                 try
                 {
-                    var value = reader.Value!.ToString();
+                    var value = reader.Value!.ToString()!;
                     return decimal.Parse(value, NumberStyles.Float, CultureInfo.InvariantCulture);
                 }
                 catch (OverflowException)
diff --git a/CryptoExchange.Net/Converters/JsonNet/BoolConverter.cs b/CryptoExchange.Net/Converters/JsonNet/BoolConverter.cs
index 4b60ee2..4f519dd 100644
--- a/CryptoExchange.Net/Converters/JsonNet/BoolConverter.cs
+++ b/CryptoExchange.Net/Converters/JsonNet/BoolConverter.cs
@@ -34,7 +34,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
         /// </returns>
         public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
         {
-            var value = reader.Value?.ToString().ToLower().Trim();
+            var value = reader.Value?.ToString()!.ToLower().Trim();
             if (value == null || value == "")
             {
                 if (Nullable.GetUnderlyingType(objectType) != null)
diff --git a/CryptoExchange.Net/Converters/JsonNet/JsonNetMessageAccessor.cs b/CryptoExchange.Net/Converters/JsonNet/JsonNetMessageAccessor.cs
index bd54ad7..2938ee4 100644
--- a/CryptoExchange.Net/Converters/JsonNet/JsonNetMessageAccessor.cs
+++ b/CryptoExchange.Net/Converters/JsonNet/JsonNetMessageAccessor.cs
@@ -297,7 +297,7 @@ namespace CryptoExchange.Net.Converters.JsonNet
 
             // Try getting the underlying byte[] instead of the ToArray to prevent creating a copy
             using var stream = MemoryMarshal.TryGetArray(data, out var arraySegment)
-                ? new MemoryStream(arraySegment.Array, arraySegment.Offset, arraySegment.Count)
+                ? new MemoryStream(arraySegment.Array!, arraySegment.Offset, arraySegment.Count)
                 : new MemoryStream(data.ToArray());
             using var reader = new StreamReader(stream, Encoding.UTF8, false, Math.Max(2, data.Length), true);
             using var jsonTextReader = new JsonTextReader(reader);
diff --git a/CryptoExchange.Net/Converters/SystemTextJson/ArrayConverter.cs b/CryptoExchange.Net/Converters/SystemTextJson/ArrayConverter.cs
index e310145..8d16480 100644
--- a/CryptoExchange.Net/Converters/SystemTextJson/ArrayConverter.cs
+++ b/CryptoExchange.Net/Converters/SystemTextJson/ArrayConverter.cs
@@ -23,7 +23,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
         public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
         {
             Type converterType = typeof(ArrayConverterInner<>).MakeGenericType(typeToConvert);
-            return (JsonConverter)Activator.CreateInstance(converterType);
+            return (JsonConverter)Activator.CreateInstance(converterType)!;
         }
 
         private class ArrayPropertyInfo
@@ -79,7 +79,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                     JsonSerializerOptions? typeOptions = null;
                     if (prop.JsonConverterType != null)
                     {
-                        var converter = (JsonConverter)Activator.CreateInstance(prop.JsonConverterType);
+                        var converter = (JsonConverter)Activator.CreateInstance(prop.JsonConverterType)!;
                         typeOptions = new JsonSerializerOptions();
                         typeOptions.Converters.Clear();
                         typeOptions.Converters.Add(converter);
@@ -90,7 +90,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                         if (prop.PropertyInfo.PropertyType == typeof(string))
                             writer.WriteStringValue(Convert.ToString(objValue, CultureInfo.InvariantCulture));
                         else
-                            writer.WriteRawValue(Convert.ToString(objValue, CultureInfo.InvariantCulture));
+                            writer.WriteRawValue(Convert.ToString(objValue, CultureInfo.InvariantCulture)!);
                     }
                     else
                     {
@@ -107,7 +107,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                 if (reader.TokenType == JsonTokenType.Null)
                     return default;
 
-                var result = Activator.CreateInstance(typeToConvert);
+                var result = Activator.CreateInstance(typeToConvert)!;
                 return (T)ParseObject(ref reader, result, typeToConvert, options);
             }
 
@@ -177,7 +177,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                         {
                             if (!_converterOptionsCache.TryGetValue(attribute.JsonConverterType, out var newOptions))
                             {
-                                var converter = (JsonConverter)Activator.CreateInstance(attribute.JsonConverterType);
+                                var converter = (JsonConverter)Activator.CreateInstance(attribute.JsonConverterType)!;
                                 newOptions = new JsonSerializerOptions
                                 {
                                     NumberHandling = SerializerOptions.WithConverters.NumberHandling,
@@ -209,7 +209,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                         }
 
                         if (targetType.IsAssignableFrom(value?.GetType()))
-                            attribute.PropertyInfo.SetValue(result, value == null ? null : value);
+                            attribute.PropertyInfo.SetValue(result, value);
                         else
                             attribute.PropertyInfo.SetValue(result, value == null ? null : Convert.ChangeType(value, targetType, CultureInfo.InvariantCulture));
                     }
diff --git a/CryptoExchange.Net/Converters/SystemTextJson/BigDecimalConverter.cs b/CryptoExchange.Net/Converters/SystemTextJson/BigDecimalConverter.cs
index 0a24dc1..4598f16 100644
--- a/CryptoExchange.Net/Converters/SystemTextJson/BigDecimalConverter.cs
+++ b/CryptoExchange.Net/Converters/SystemTextJson/BigDecimalConverter.cs
@@ -17,7 +17,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
             {
                 try
                 {
-                    return decimal.Parse(reader.GetString(), NumberStyles.Float, CultureInfo.InvariantCulture);
+                    return decimal.Parse(reader.GetString()!, NumberStyles.Float, CultureInfo.InvariantCulture);
                 }
                 catch(OverflowException)
                 {
diff --git a/CryptoExchange.Net/Converters/SystemTextJson/BoolConverter.cs b/CryptoExchange.Net/Converters/SystemTextJson/BoolConverter.cs
index 50df293..2f45135 100644
--- a/CryptoExchange.Net/Converters/SystemTextJson/BoolConverter.cs
+++ b/CryptoExchange.Net/Converters/SystemTextJson/BoolConverter.cs
@@ -21,7 +21,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
         public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
         {
             Type converterType = typeof(BoolConverterInner<>).MakeGenericType(typeToConvert);
-            return (JsonConverter)Activator.CreateInstance(converterType);
+            return (JsonConverter)Activator.CreateInstance(converterType)!;
         }
 
         private class BoolConverterInner<T> : JsonConverter<T>
diff --git a/CryptoExchange.Net/Converters/SystemTextJson/DateTimeConverter.cs b/CryptoExchange.Net/Converters/SystemTextJson/DateTimeConverter.cs
index bfb0bfb..1035e2d 100644
--- a/CryptoExchange.Net/Converters/SystemTextJson/DateTimeConverter.cs
+++ b/CryptoExchange.Net/Converters/SystemTextJson/DateTimeConverter.cs
@@ -27,7 +27,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
         public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
         {
             Type converterType = typeof(DateTimeConverterInner<>).MakeGenericType(typeToConvert);
-            return (JsonConverter)Activator.CreateInstance(converterType);
+            return (JsonConverter)Activator.CreateInstance(converterType)!;
         }
 
         private class DateTimeConverterInner<T> : JsonConverter<T>
@@ -74,7 +74,9 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
             public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
             {
                 if (value == null)
+                {
                     writer.WriteNullValue();
+                }
                 else
                 {
                     var dtValue = (DateTime)(object)value;
diff --git a/CryptoExchange.Net/Converters/SystemTextJson/JsonConverterCtorAttribute.cs b/CryptoExchange.Net/Converters/SystemTextJson/JsonConverterCtorAttribute.cs
index c831ea8..c58c0e3 100644
--- a/CryptoExchange.Net/Converters/SystemTextJson/JsonConverterCtorAttribute.cs
+++ b/CryptoExchange.Net/Converters/SystemTextJson/JsonConverterCtorAttribute.cs
@@ -24,7 +24,7 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
         /// <inheritdoc />
         public override JsonConverter CreateConverter(Type typeToConvert)
         {
-            return (JsonConverter)Activator.CreateInstance(_type, _parameters);
+            return (JsonConverter)Activator.CreateInstance(_type, _parameters)!;
         }
     }
 
diff --git a/CryptoExchange.Net/CryptoExchange.Net.csproj b/CryptoExchange.Net/CryptoExchange.Net.csproj
index 76dc198..64929ef 100644
--- a/CryptoExchange.Net/CryptoExchange.Net.csproj
+++ b/CryptoExchange.Net/CryptoExchange.Net.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net9.0</TargetFrameworks>
   </PropertyGroup>
   <PropertyGroup>
     <PackageId>CryptoExchange.Net</PackageId>
diff --git a/CryptoExchange.Net/ExtensionMethods.cs b/CryptoExchange.Net/ExtensionMethods.cs
index 4c14859..363959c 100644
--- a/CryptoExchange.Net/ExtensionMethods.cs
+++ b/CryptoExchange.Net/ExtensionMethods.cs
@@ -67,7 +67,7 @@ namespace CryptoExchange.Net
             {
                 if (serializationType == ArrayParametersSerialization.Array)
                 {
-                    uriString += $"{string.Join("&", ((object[])(urlEncodeValues ? Uri.EscapeDataString(arrayEntry.Value.ToString()) : arrayEntry.Value)).Select(v => $"{arrayEntry.Key}[]={string.Format(CultureInfo.InvariantCulture, "{0}", v)}"))}&";
+                    uriString += $"{string.Join("&", ((object[])(urlEncodeValues ? Uri.EscapeDataString(arrayEntry.Value.ToString()!) : arrayEntry.Value)).Select(v => $"{arrayEntry.Key}[]={string.Format(CultureInfo.InvariantCulture, "{0}", v)}"))}&";
                 }
                 else if (serializationType == ArrayParametersSerialization.MultipleValues)
                 {
@@ -111,7 +111,7 @@ namespace CryptoExchange.Net
                     formData.Add(kvp.Key, string.Format(CultureInfo.InvariantCulture, "{0}", kvp.Value));
                 }
             }
-            return formData.ToString();
+            return formData.ToString()!;
         }
 
         /// <summary>
@@ -366,7 +366,7 @@ namespace CryptoExchange.Net
         {
             using var decompressedStream = new MemoryStream();
             using var dataStream = MemoryMarshal.TryGetArray(data, out var arraySegment)
-                ? new MemoryStream(arraySegment.Array, arraySegment.Offset, arraySegment.Count)
+                ? new MemoryStream(arraySegment.Array!, arraySegment.Offset, arraySegment.Count)
                 : new MemoryStream(data.ToArray());
             using var deflateStream = new GZipStream(new MemoryStream(data.ToArray()), CompressionMode.Decompress);
             deflateStream.CopyTo(decompressedStream);
diff --git a/CryptoExchange.Net/Objects/ByteOrderComparer.cs b/CryptoExchange.Net/Objects/ByteOrderComparer.cs
index 7ad3cbd..e2b694b 100644
--- a/CryptoExchange.Net/Objects/ByteOrderComparer.cs
+++ b/CryptoExchange.Net/Objects/ByteOrderComparer.cs
@@ -14,7 +14,7 @@ namespace CryptoExchange.Net.Objects
         /// <param name="x"></param>
         /// <param name="y"></param>
         /// <returns></returns>
-        public int Compare(byte[] x, byte[] y)
+        public int Compare(byte[]? x, byte[]? y)
         {
             // Shortcuts: If both are null, they are the same.
             if (x == null && y == null) return 0;
diff --git a/CryptoExchange.Net/Objects/OrderedStringComparer.cs b/CryptoExchange.Net/Objects/OrderedStringComparer.cs
index 15e9b2d..9dfe067 100644
--- a/CryptoExchange.Net/Objects/OrderedStringComparer.cs
+++ b/CryptoExchange.Net/Objects/OrderedStringComparer.cs
@@ -13,7 +13,7 @@ namespace CryptoExchange.Net.Objects
         /// <param name="x"></param>
         /// <param name="y"></param>
         /// <returns></returns>
-        public int Compare(string x, string y)
+        public int Compare(string? x, string? y)
         {
             // Shortcuts: If both are null, they are the same.
             if (x == null && y == null) return 0;
diff --git a/CryptoExchange.Net/Objects/ParameterCollection.cs b/CryptoExchange.Net/Objects/ParameterCollection.cs
index 71b1378..599067e 100644
--- a/CryptoExchange.Net/Objects/ParameterCollection.cs
+++ b/CryptoExchange.Net/Objects/ParameterCollection.cs
@@ -156,7 +156,7 @@ namespace CryptoExchange.Net.Objects
         /// <param name="value"></param>
         public void AddSecondsString(string key, DateTime value)
         {
-            Add(key, DateTimeConverter.ConvertToSeconds(value).ToString());
+            Add(key, DateTimeConverter.ConvertToSeconds(value).ToString()!);
         }
 
         /// <summary>
@@ -167,7 +167,7 @@ namespace CryptoExchange.Net.Objects
         public void AddOptionalSecondsString(string key, DateTime? value)
         {
             if (value != null)
-                Add(key, DateTimeConverter.ConvertToSeconds(value).ToString());
+                Add(key, DateTimeConverter.ConvertToSeconds(value).ToString()!);
         }
 
         /// <summary>
@@ -187,7 +187,7 @@ namespace CryptoExchange.Net.Objects
         /// <param name="value"></param>
         public void AddEnumAsInt<T>(string key, T value)
         {
-            var stringVal = EnumConverter.GetString(value);
+            var stringVal = EnumConverter.GetString(value)!;
             Add(key, int.Parse(stringVal)!);
         }
 
diff --git a/CryptoExchange.Net/OrderBook/SymbolOrderBook.cs b/CryptoExchange.Net/OrderBook/SymbolOrderBook.cs
index c85d707..bcd72a0 100644
--- a/CryptoExchange.Net/OrderBook/SymbolOrderBook.cs
+++ b/CryptoExchange.Net/OrderBook/SymbolOrderBook.cs
@@ -843,9 +843,9 @@ namespace CryptoExchange.Net.OrderBook
 
     internal class DescComparer<T> : IComparer<T>
     {
-        public int Compare(T x, T y)
+        public int Compare(T? x, T? y)
         {
-            return Comparer<T>.Default.Compare(y, x);
+            return Comparer<T>.Default.Compare(y!, x!);
         }
     }
 }
diff --git a/CryptoExchange.Net/RateLimiting/Guards/RateLimitGuard.cs b/CryptoExchange.Net/RateLimiting/Guards/RateLimitGuard.cs
index 385f065..810fca7 100644
--- a/CryptoExchange.Net/RateLimiting/Guards/RateLimitGuard.cs
+++ b/CryptoExchange.Net/RateLimiting/Guards/RateLimitGuard.cs
@@ -20,7 +20,7 @@ namespace CryptoExchange.Net.RateLimiting.Guards
         /// <summary>
         /// Apply guard per connection
         /// </summary>
-        public static Func<RequestDefinition, string, string?, string> PerConnection { get; } = new Func<RequestDefinition, string, string?, string>((def, host, key) => def.ConnectionId.ToString());
+        public static Func<RequestDefinition, string, string?, string> PerConnection { get; } = new Func<RequestDefinition, string, string?, string>((def, host, key) => def.ConnectionId.ToString()!);
         /// <summary>
         /// Apply guard per API key
         /// </summary>
diff --git a/CryptoExchange.Net/Requests/Request.cs b/CryptoExchange.Net/Requests/Request.cs
index b2db821..f73b0fc 100644
--- a/CryptoExchange.Net/Requests/Request.cs
+++ b/CryptoExchange.Net/Requests/Request.cs
@@ -48,7 +48,7 @@ namespace CryptoExchange.Net.Requests
         }
 
         /// <inheritdoc />
-        public Uri Uri => _request.RequestUri;
+        public Uri Uri => _request.RequestUri!;
 
         /// <inheritdoc />
         public int RequestId { get; }
diff --git a/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/EndpointOptions.cs b/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/EndpointOptions.cs
index 594a4bd..bd28507 100644
--- a/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/EndpointOptions.cs
+++ b/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/EndpointOptions.cs
@@ -60,8 +60,8 @@ namespace CryptoExchange.Net.SharedApis
                 }
                 else
                 {
-                    if (param.Names.All(x => ExchangeParameters.HasValue(exchangeParameters, exchange, x, param.ValueType) != true))
-                        return new ArgumentError($"One of exchange parameters `{string.Join(", ", param.Names)}` for exchange `{exchange}` should be provided. Example: {param.ExampleValue}");
+                    if (param.Names!.All(x => ExchangeParameters.HasValue(exchangeParameters, exchange, x, param.ValueType) != true))
+                        return new ArgumentError($"One of exchange parameters `{string.Join(", ", param.Names!)}` for exchange `{exchange}` should be provided. Example: {param.ExampleValue}");
                 }
             }
 
@@ -113,13 +113,13 @@ namespace CryptoExchange.Net.SharedApis
             {
                 if (!string.IsNullOrEmpty(param.Name))
                 {
-                    if (typeof(T).GetProperty(param.Name).GetValue(request, null) == null)
+                    if (typeof(T).GetProperty(param.Name)!.GetValue(request, null) == null)
                         return new ArgumentError($"Required optional parameter `{param.Name}` for exchange `{exchange}` is missing. Example: {param.ExampleValue}");
                 }
                 else
                 {
-                    if (param.Names.All(x => typeof(T).GetProperty(param.Name).GetValue(request, null) == null))
-                        return new ArgumentError($"One of optional parameters `{string.Join(", ", param.Names)}` for exchange `{exchange}` should be provided. Example: {param.ExampleValue}");
+                    if (param.Names!.All(x => typeof(T).GetProperty(param.Name!)!.GetValue(request, null) == null))
+                        return new ArgumentError($"One of optional parameters `{string.Join(", ", param.Names!)}` for exchange `{exchange}` should be provided. Example: {param.ExampleValue}");
                 }
 
             }
diff --git a/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/GetOrderBookOptions.cs b/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/GetOrderBookOptions.cs
index 2b59714..12e2745 100644
--- a/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/GetOrderBookOptions.cs
+++ b/CryptoExchange.Net/SharedApis/Models/Options/Endpoints/GetOrderBookOptions.cs
@@ -64,7 +64,7 @@ namespace CryptoExchange.Net.SharedApis
         public override string ToString(string exchange)
         {
             var sb = new StringBuilder(base.ToString(exchange));
-            sb.AppendLine($"Supported limit values: [{(SupportedLimits == null ? string.Join(", ", SupportedLimits) : $"{MinLimit}..{MaxLimit}")}]");
+            sb.AppendLine($"Supported limit values: [{(SupportedLimits != null ? string.Join(", ", SupportedLimits) : $"{MinLimit}..{MaxLimit}")}]");
             return sb.ToString();
         }
     }
diff --git a/CryptoExchange.Net/SharedApis/Models/Options/ParameterDescription.cs b/CryptoExchange.Net/SharedApis/Models/Options/ParameterDescription.cs
index 7636556..8a5dc57 100644
--- a/CryptoExchange.Net/SharedApis/Models/Options/ParameterDescription.cs
+++ b/CryptoExchange.Net/SharedApis/Models/Options/ParameterDescription.cs
@@ -55,7 +55,7 @@ namespace CryptoExchange.Net.SharedApis
         {
             if (Name != null)
                 return $"[{ValueType.Name}] {Name}: {Description} | example: {ExampleValue}";
-            return $"[{ValueType.Name}] {string.Join(" / ", Names)}: {Description} | example: {ExampleValue}";
+            return $"[{ValueType.Name}] {string.Join(" / ", Names!)}: {Description} | example: {ExampleValue}";
         }
     }
 }
diff --git a/CryptoExchange.Net/Sockets/CryptoExchangeWebSocketClient.cs b/CryptoExchange.Net/Sockets/CryptoExchangeWebSocketClient.cs
index 1d364eb..2d8ef04 100644
--- a/CryptoExchange.Net/Sockets/CryptoExchangeWebSocketClient.cs
+++ b/CryptoExchange.Net/Sockets/CryptoExchangeWebSocketClient.cs
@@ -195,9 +195,12 @@ namespace CryptoExchange.Net.Sockets
                     socket.Options.SetBuffer(_receiveBufferSize, _sendBufferSize);
                 if (Parameters.Proxy != null)
                     SetProxy(socket, Parameters.Proxy);
-                #if NET6_0_OR_GREATER
+#if NET6_0_OR_GREATER
                 socket.Options.CollectHttpResponseDetails = true;
-                #endif
+#endif
+#if NET9_0_OR_GREATER
+                socket.Options.KeepAliveTimeout = TimeSpan.FromSeconds(10);
+#endif
             }
             catch (PlatformNotSupportedException)
             {
@@ -235,13 +238,13 @@ namespace CryptoExchange.Net.Sockets
 
                 if (e is WebSocketException we)
                 {
-                    #if (NET6_0_OR_GREATER)
+#if (NET6_0_OR_GREATER)
                     if (_socket.HttpStatusCode == HttpStatusCode.TooManyRequests)
                     {
                         await (OnConnectRateLimited?.Invoke() ?? Task.CompletedTask).ConfigureAwait(false);
                         return new CallResult(new ServerRateLimitError(we.Message));
                     }
-                    #else
+#else
                     // ClientWebSocket.HttpStatusCode is only available in .NET6+ https://learn.microsoft.com/en-us/dotnet/api/system.net.websockets.clientwebsocket.httpstatuscode?view=net-8.0
                     // Try to read 429 from the message instead
                     if (we.Message.Contains("429"))
@@ -249,7 +252,7 @@ namespace CryptoExchange.Net.Sockets
                         await (OnConnectRateLimited?.Invoke() ?? Task.CompletedTask).ConfigureAwait(false);
                         return new CallResult(new ServerRateLimitError(we.Message));
                     }
-                    #endif
+#endif
                 }
 
                 return new CallResult(new CantConnectError());
@@ -604,14 +607,14 @@ namespace CryptoExchange.Net.Sockets
                             if (_socket.State == WebSocketState.CloseReceived)
                             {
                                 // Close received means it server initiated, we should send a confirmation and close the socket
-                                _logger.SocketReceivedCloseMessage(Id, receiveResult.CloseStatus.ToString(), receiveResult.CloseStatusDescription);
+                                _logger.SocketReceivedCloseMessage(Id, receiveResult.CloseStatus.ToString()!, receiveResult.CloseStatusDescription ?? string.Empty);
                                 if (_closeTask?.IsCompleted != false)
                                     _closeTask = CloseInternalAsync();
                             }
                             else
                             {
                                 // Means the socket is now closed and we were the one initiating it
-                                _logger.SocketReceivedCloseConfirmation(Id, receiveResult.CloseStatus.ToString(), receiveResult.CloseStatusDescription);
+                                _logger.SocketReceivedCloseConfirmation(Id, receiveResult.CloseStatus.ToString()!, receiveResult.CloseStatusDescription ?? string.Empty);
                             }
 
                             break;
@@ -626,7 +629,7 @@ namespace CryptoExchange.Net.Sockets
                             // Write the data to a memory stream to be reassembled later
                             if (multipartStream == null)
                                 multipartStream = new MemoryStream();
-                            multipartStream.Write(buffer.Array, buffer.Offset, receiveResult.Count);
+                            multipartStream.Write(buffer.Array!, buffer.Offset, receiveResult.Count);
                         }
                         else
                         {
@@ -640,7 +643,7 @@ namespace CryptoExchange.Net.Sockets
                             {
                                 // Received the end of a multipart message, write to memory stream for reassembling
                                 _logger.SocketReceivedPartialMessage(Id, receiveResult.Count);
-                                multipartStream!.Write(buffer.Array, buffer.Offset, receiveResult.Count);
+                                multipartStream!.Write(buffer.Array!, buffer.Offset, receiveResult.Count);
                             }
 
                             break;
diff --git a/CryptoExchange.Net/Sockets/SocketConnection.cs b/CryptoExchange.Net/Sockets/SocketConnection.cs
index a1deaaa..e844272 100644
--- a/CryptoExchange.Net/Sockets/SocketConnection.cs
+++ b/CryptoExchange.Net/Sockets/SocketConnection.cs
@@ -398,7 +398,7 @@ namespace CryptoExchange.Net.Sockets
         /// <returns></returns>
         protected virtual Task HandleRequestRateLimitedAsync(int requestId)
         {
-            Query query;
+            Query? query;
             lock (_listenersLock)
             {
                 query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
@@ -427,7 +427,7 @@ namespace CryptoExchange.Net.Sockets
         /// <param name="requestId">Id of the request sent</param>
         protected virtual Task HandleRequestSentAsync(int requestId)
         {
-            Query query;
+            Query? query;
             lock (_listenersLock)
             {
                 query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
diff --git a/CryptoExchange.Net/Testing/Comparers/JsonNetComparer.cs b/CryptoExchange.Net/Testing/Comparers/JsonNetComparer.cs
index 3c317e4..4d7b3ad 100644
--- a/CryptoExchange.Net/Testing/Comparers/JsonNetComparer.cs
+++ b/CryptoExchange.Net/Testing/Comparers/JsonNetComparer.cs
@@ -378,7 +378,7 @@ namespace CryptoExchange.Net.Testing.Comparers
                 if (objectValue is bool boolVal && jsonValue.Value<bool>() != boolVal)
                     throw new Exception($"{method}: {property} not equal: {jsonValue.Value<bool>()} vs {(bool)objectValue}");
 
-                if (jsonValue.Value<bool>() != bool.Parse(objectValue.ToString()))
+                if (jsonValue.Value<bool>() != bool.Parse(objectValue.ToString()!))
                     throw new Exception($"{method}: {property} not equal: {jsonValue.Value<bool>()} vs {(bool)objectValue}");
             }
         }
diff --git a/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs b/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
index 871127a..4ee5b87 100644
--- a/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
+++ b/CryptoExchange.Net/Testing/Comparers/SystemTextJsonComparer.cs
@@ -211,7 +211,7 @@ namespace CryptoExchange.Net.Testing.Comparers
 
                     if (dictProp.Value.Type == JTokenType.Object)
                     {
-                        CheckPropertyValue(method, dictProp.Value, dict[dictProp.Name]!, dict[dictProp.Name].GetType(), null, null, ignoreProperties);
+                        CheckPropertyValue(method, dictProp.Value, dict[dictProp.Name]!, dict[dictProp.Name]!.GetType(), null, null, ignoreProperties);
                     }
                     else
                     {
diff --git a/CryptoExchange.Net/Testing/EnumValueTraceListener.cs b/CryptoExchange.Net/Testing/EnumValueTraceListener.cs
index ce19264..3b13193 100644
--- a/CryptoExchange.Net/Testing/EnumValueTraceListener.cs
+++ b/CryptoExchange.Net/Testing/EnumValueTraceListener.cs
@@ -5,8 +5,11 @@ namespace CryptoExchange.Net.Testing
 {
     internal class EnumValueTraceListener : TraceListener
     {
-        public override void Write(string message)
+        public override void Write(string? message)
         {
+            if (message == null)
+                return;
+
             if (message.Contains("Cannot map"))
                 throw new Exception("Enum value error: " + message);
 
@@ -14,8 +17,11 @@ namespace CryptoExchange.Net.Testing
                 throw new Exception("Enum null error: " + message);
         }
 
-        public override void WriteLine(string message)
+        public override void WriteLine(string? message)
         {
+            if (message == null)
+                return;
+
             if (message.Contains("Cannot map"))
                 throw new Exception("Enum value error: " + message);
 
diff --git a/CryptoExchange.Net/Testing/TestHelpers.cs b/CryptoExchange.Net/Testing/TestHelpers.cs
index 0f91d44..532dbbe 100644
--- a/CryptoExchange.Net/Testing/TestHelpers.cs
+++ b/CryptoExchange.Net/Testing/TestHelpers.cs
@@ -169,7 +169,7 @@ namespace CryptoExchange.Net.Testing
         {
             var assembly = Assembly.GetAssembly(clientType);
             var interfaceType = clientType.GetInterface("I" + clientType.Name);
-            var clientInterfaces = assembly.GetTypes().Where(t => t.Name.StartsWith("I" + clientType.Name) && !t.Name.EndsWith("Shared"));
+            var clientInterfaces = assembly!.GetTypes().Where(t => t.Name.StartsWith("I" + clientType.Name) && !t.Name.EndsWith("Shared"));
 
             foreach (var clientInterface in clientInterfaces)
             {
@@ -179,9 +179,7 @@ namespace CryptoExchange.Net.Testing
                     int methods = 0;
                     foreach (var method in implementation.GetMethods().Where(m => implementationTypes.IsAssignableFrom(m.ReturnType)))
                     {
-                        var interfaceMethod = clientInterface.GetMethod(method.Name, method.GetParameters().Select(p => p.ParameterType).ToArray());
-                        if (interfaceMethod == null)
-                            throw new Exception($"Missing interface for method {method.Name} in {implementation.Name} implementing interface {clientInterface.Name}");
+                        var interfaceMethod = clientInterface.GetMethod(method.Name, method.GetParameters().Select(p => p.ParameterType).ToArray()) ?? throw new Exception($"Missing interface for method {method.Name} in {implementation.Name} implementing interface {clientInterface.Name}");
                         methods++;
                     }