NewtonSoft.Json Treating Blank Value as Null but not throwing error

Question

Environment

• .net 7
• Using Both System.Text.Json
• Also NewtonSoft.Json ( 13.0.2)

Example code

string str = @"{
    ""DateTimeNull"":""""
}";
try
{
    var t = System.Text.Json.JsonSerializer.Deserialize<Test>(str);
}
catch (JsonException ex) 
{
    Console.WriteLine(new { Field = ex.Path , Message = ex.Message });
}

try
{
    var t = Newtonsoft.Json.JsonConvert.DeserializeObject<Test>(str);
}
catch (Exception ex)
{
    Console.WriteLine(ex.Message);
}

public class Test
{
    public DateTime? DateTimeNull { get; set; }
}

In above System.Text.Json Deserlizer throw exception but newtonsoft.json line is not throwing any exception. It is converting empty value to null but I want it should thow error and due to limitation I can not move to System.Text.Json as of now.

• Payload ( This is i already set in str)
• Sample one

@"{
    ""DateTimeNull"":""""
}";

Expected result: Throw error and should not convert to null.

• Sample two.

@"{
    ""DateTimeNull"": null
}";

Expected result: Should not throw error and it is null value and destination type is null.

Answer 1

I usually recommend to use a JsonConstructor:

var json = @"{
    ""DateTimeNull"":""""
}";

Test test = JsonConvert.DeserializeObject<Test>(json);

public class Test
{
    public DateTime? DateTimeNull { get; set; }
    
    [Newtonsoft.Json.JsonConstructor]
    public Test(JToken DateTimeNull)
    {
        if (DateTimeNull.Type == JTokenType.Null) this.DateTimeNull = null;
        else if ((string)DateTimeNull == string.Empty)
            throw new JsonException("DateTimeNull property should not be an empty string");
        else this.DateTimeNull = DateTimeNull.ToObject<DateTime>();
    }
}