A converter that inherits JsonConverter<object> doesn't work on properties of nullable value type #36329
Description
If I create a converter that inherits from JsonConverter<object>, it can be applied to a property of type Int32, but not to a property of type Nullable<Int32>. It throws:
InvalidCastException: Unable to cast object of type 'HexIntegerConverter' to type
'System.Text.Json.Serialization.JsonConverter`1[System.Nullable`1[System.Int32]]'.
Repro (in LinqPad)
void Main()
{
var foo = new Foo { IntProperty = 123, NullableIntProperty = 456 };
var fooJson = JsonSerializer.Serialize(foo).Dump();
JsonSerializer.Deserialize<Foo>(fooJson).Dump();
}
class Foo
{
[JsonConverter(typeof(HexIntegerConverter))]
public int IntProperty { get; set; }
[JsonConverter(typeof(HexIntegerConverter))]
public int? NullableIntProperty { get; set; }
}
// Serializes an int to an hex string
class HexIntegerConverter : JsonConverter<object>
{
public override object Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
{
var s = reader.GetString();
if (string.IsNullOrEmpty(s))
{
if (typeToConvert == typeof(int))
return 0;
else
return null;
}
return int.Parse(s, System.Globalization.NumberStyles.HexNumber);
}
public override void Write(Utf8JsonWriter writer, object value, JsonSerializerOptions options)
{
if (value is null)
{
writer.WriteNullValue();
}
else
{
writer.WriteStringValue(((int)value).ToString("x"));
}
}
public override bool CanConvert(Type typeToConvert)
{
return typeToConvert == typeof(int) || typeToConvert == typeof(int?);
}
}This code throws the exception above. If I remove the converter from the nullable property, it works as expected.
This looks like a bug to me. Why is it trying to cast to a JsonSerializer<int?>? It doesn't do that for the non-nullable property...