Added converters/handling for values too big to fit decimal

CryptoExchange.Net.UnitTests/SystemTextJsonConverterTests.cs

@@ -214,6 +214,41 @@ namespace CryptoExchange.Net.UnitTests
             var output = JsonSerializer.Deserialize<NotNullableSTJBoolObject>($"{{ \"Value\": {val} }}");
             Assert.That(output.Value == expected);
         }
+
+        [TestCase("1", 1)]
+        [TestCase("1.1", 1.1)]
+        [TestCase("-1.1", -1.1)]
+        [TestCase(null, null)]
+        [TestCase("", null)]
+        [TestCase("null", null)]
+        [TestCase("1E+2", 100)]
+        [TestCase("1E-2", 0.01)]
+        [TestCase("80228162514264337593543950335", -999)] // -999 is workaround for not being able to specify decimal.MaxValue
+        public void TestDecimalConverterString(string value, decimal? expected)
+        {
+            var result = JsonSerializer.Deserialize<STJDecimalObject>("{ \"test\": \""+ value + "\"}");
+            Assert.That(result.Test, Is.EqualTo(expected == -999 ? decimal.MaxValue : expected));
+        }
+
+        [TestCase("1", 1)]
+        [TestCase("1.1", 1.1)]
+        [TestCase("-1.1", -1.1)]
+        [TestCase("null", null)]
+        [TestCase("1E+2", 100)]
+        [TestCase("1E-2", 0.01)]
+        [TestCase("80228162514264337593543950335", -999)] // -999 is workaround for not being able to specify decimal.MaxValue
+        public void TestDecimalConverterNumber(string? value, decimal? expected)
+        {
+            var result = JsonSerializer.Deserialize<STJDecimalObject>("{ \"test\": " + value + "}");
+            Assert.That(result.Test, Is.EqualTo(expected == -999 ? decimal.MaxValue : expected));
+        }
+    }
+
+    public class STJDecimalObject
+    {
+        [JsonConverter(typeof(DecimalConverter))]
+        [JsonPropertyName("test")]
+        public decimal? Test { get; set; }
     }
 
     public class STJTimeObject

CryptoExchange.Net/Converters/JsonNet/BigDecimalConverter.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Globalization;
+using Newtonsoft.Json;
+
+namespace CryptoExchange.Net.Converters.JsonNet
+{
+    /// <summary>
+    /// Decimal converter that handles overflowing decimal values (by setting it to decimal.MaxValue)
+    /// </summary>
+    public class BigDecimalConverter : JsonConverter
+    {
+        /// <inheritdoc />
+        public override bool CanConvert(Type objectType)
+        {
+            if (Nullable.GetUnderlyingType(objectType) != null)
+                return Nullable.GetUnderlyingType(objectType) == typeof(decimal);
+            return objectType == typeof(decimal);
+        }
+
+        /// <inheritdoc />
+        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
+        {
+            if (reader.TokenType == JsonToken.Null)
+                return null;
+
+            if (reader.TokenType == JsonToken.Float || reader.TokenType == JsonToken.Integer)
+            {
+                try
+                {
+                    return decimal.Parse(reader.Value!.ToString(), NumberStyles.Float, CultureInfo.InvariantCulture);
+                }
+                catch (OverflowException) 
+                {
+                    // Value doesn't fit decimal; set it to max value
+                    return decimal.MaxValue;
+                }
+            }
+
+            if (reader.TokenType == JsonToken.String)
+            {
+                try
+                {
+                    var value = reader.Value!.ToString();
+                    return decimal.Parse(value, NumberStyles.Float, CultureInfo.InvariantCulture);
+                }
+                catch (OverflowException)
+                {
+                    // Value doesn't fit decimal; set it to max value
+                    return decimal.MaxValue;
+                }
+            }
+
+            return null;
+        }
+
+        /// <inheritdoc />
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer)
+        {
+            writer.WriteValue(value);
+        }
+    }
+}

CryptoExchange.Net/Converters/SystemTextJson/BigDecimalConverter.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace CryptoExchange.Net.Converters.SystemTextJson
+{
+    /// <summary>
+    /// Decimal converter that handles overflowing decimal values (by setting it to decimal.MaxValue)
+    /// </summary>
+    public class BigDecimalConverter : JsonConverter<decimal>
+    {
+        /// <inheritdoc />
+        public override decimal Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            if (reader.TokenType == JsonTokenType.String)
+            {
+                try
+                {
+                    return decimal.Parse(reader.GetString(), NumberStyles.Float, CultureInfo.InvariantCulture);
+                }
+                catch(OverflowException)
+                {
+                    // Value doesn't fit decimal, default to max value
+                    return decimal.MaxValue;
+                }
+            }
+
+            try
+            {
+                return reader.GetDecimal();
+            }
+            catch(FormatException)
+            {
+                // Format issue, assume value is too large
+                return decimal.MaxValue;
+            }
+        }
+
+        /// <inheritdoc />
+        public override void Write(Utf8JsonWriter writer, decimal value, JsonSerializerOptions options)
+        {
+            writer.WriteNumberValue(value);
+        }
+    }
+}

CryptoExchange.Net/Converters/SystemTextJson/DecimalConverter.cs

@@ -22,10 +22,26 @@ namespace CryptoExchange.Net.Converters.SystemTextJson
                 if (string.IsNullOrEmpty(value) || string.Equals("null", value))
                     return null;
 
-                return decimal.Parse(value, NumberStyles.Float, CultureInfo.InvariantCulture);
+                try
+                {
+                    return decimal.Parse(value, NumberStyles.Float, CultureInfo.InvariantCulture);
+                }
+                catch(OverflowException)
+                {
+                    // Value doesn't fit decimal, default to max value
+                    return decimal.MaxValue;
+                }
             }
 
-            return reader.GetDecimal();
+            try
+            {
+                return reader.GetDecimal();
+            }
+            catch(FormatException)
+            {
+                // Format issue, assume value is too large
+                return decimal.MaxValue;
+            }
         }
 
         /// <inheritdoc />