diff --git a/CryptoExchange.Net/Converters/SystemTextJson/CommaSplitStringConverter.cs b/CryptoExchange.Net/Converters/SystemTextJson/CommaSplitStringConverter.cs
new file mode 100644
index 0000000..b3ec015
--- /dev/null
+++ b/CryptoExchange.Net/Converters/SystemTextJson/CommaSplitStringConverter.cs
@@ -0,0 +1,30 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace CryptoExchange.Net.Converters.SystemTextJson
+{
+    /// <summary>
+    /// Converter for comma separated string values
+    /// </summary>
+    public class CommaSplitStringConverter : JsonConverter<string[]>
+    {
+        /// <inheritdoc />
+        public override string[]? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var str = reader.GetString();
+            if (string.IsNullOrEmpty(str))
+                return [];
+
+            return str!.Split(',').ToArray() ?? [];
+        }
+
+        /// <inheritdoc />
+        public override void Write(Utf8JsonWriter writer, string[] value, JsonSerializerOptions options)
+        {
+            writer.WriteStringValue(string.Join(",", value));
+        }
+    }
+}
diff --git a/CryptoExchange.Net/ExtensionMethods.cs b/CryptoExchange.Net/ExtensionMethods.cs
index 6f78e63..7dd272c 100644
--- a/CryptoExchange.Net/ExtensionMethods.cs
+++ b/CryptoExchange.Net/ExtensionMethods.cs
@@ -74,8 +74,13 @@ namespace CryptoExchange.Net
                 {
                     if (serializationType == ArrayParametersSerialization.Array)
                     {
-                        foreach(var entry in (object[])parameter.Value)
+                        bool firstArrayValue = true;
+                        foreach (var entry in (object[])parameter.Value)
                         {
+                            if (!firstArrayValue)
+                                uriString.Append('&');
+                            firstArrayValue = false;
+
                             uriString.Append(parameter.Key);
                             uriString.Append("[]=");
                             if (urlEncodeValues)
@@ -611,6 +616,26 @@ namespace CryptoExchange.Net
 
             return services;
         }
+
+        /// <summary>
+        /// Convert a hex encoded string to byte array
+        /// </summary>
+        /// <param name="hexString"></param>
+        /// <returns></returns>
+        public static byte[] HexStringToBytes(this string hexString)
+        {
+            if (hexString.StartsWith("0x"))
+                hexString = hexString.Substring(2);
+
+            byte[] bytes = new byte[hexString.Length / 2];
+            for (int i = 0; i < hexString.Length; i += 2)
+            {
+                string hexSubstring = hexString.Substring(i, 2);
+                bytes[i / 2] = Convert.ToByte(hexSubstring, 16);
+            }
+
+            return bytes;
+        }
     }
 }
 
diff --git a/CryptoExchange.Net/Objects/ParameterCollection.cs b/CryptoExchange.Net/Objects/ParameterCollection.cs
index daa011d..d49f8fa 100644
--- a/CryptoExchange.Net/Objects/ParameterCollection.cs
+++ b/CryptoExchange.Net/Objects/ParameterCollection.cs
@@ -96,6 +96,23 @@ namespace CryptoExchange.Net.Objects
                 base.Add(key, value.Value.ToString(CultureInfo.InvariantCulture));
         }
 
+        /// <summary>
+        /// Add a DateTime value as string
+        /// </summary>
+        public void AddString(string key, DateTime value)
+        {
+            base.Add(key, value.ToString("yyyy-MM-ddTHH:mm:ssZ"));
+        }
+
+        /// <summary>
+        /// Add a DateTime value as string. Not added if value is null
+        /// </summary>
+        public void AddOptionalString(string key, DateTime? value)
+        {
+            if (value != null)
+                base.Add(key, value.Value.ToString("yyyy-MM-ddTHH:mm:ssZ"));
+        }
+
         /// <summary>
         /// Add a datetime value as milliseconds timestamp
         /// </summary>
@@ -241,6 +258,45 @@ namespace CryptoExchange.Net.Objects
                 base.Add(key, int.Parse(stringVal));
             }
         }
+        
+        /// <summary>
+        /// Add key as comma separated values
+        /// </summary>
+        public void AddCommaSeparated(string key, IEnumerable<string> values)
+        {
+            base.Add(key, string.Join(",", values));
+        }
+
+        /// <summary>
+        /// Add key as comma separated values if there are values provided
+        /// </summary>
+        public void AddOptionalCommaSeparated(string key, IEnumerable<string>? values)
+        {
+            if (values == null || !values.Any())
+                return;
+
+            base.Add(key, string.Join(",", values));
+        }
+
+        /// <summary>
+        /// Add key as boolean lower case value
+        /// </summary>
+        public void AddBoolString(string key, bool value)
+        {
+            base.Add(key, value.ToString().ToLower());
+        }
+
+        /// <summary>
+        /// Add key as boolean lower case value if it's not null
+        /// </summary>
+        public void AddOptionalBoolString(string key, bool? value)
+        {
+            if (value == null)
+                return;
+
+            base.Add(key, value.ToString()!.ToLower());
+        }
+
 
         /// <summary>
         /// Set the request body. Can be used to specify a simple value or array as the body instead of an object