Using JsonConverter to keep all datetime values formatted the same - datetime

Question

I have a use case in which ALL date/time values must be saved in JSON documents using the following format:
yyyy-MM-ddTHH:mm:ss.fffffff
In other words, all date/time values will be exactly 27 characters in length regardless of the date/time value, for example:
System.DateTime.MinValue = "0001-01-01T00:00:00.0000000"
System.DateTime.MaxValue = "9999-12-31T23:59:59.9999999"
19-May-2018 10:35:12 am = "2018-05-19T10:35:12.0000000"
Unfortunately, Json.Net decides to format date/times in various formats depending on the date/time value. I have tried to use the JsonConverter attribute on date/time properties, ie:
[JsonConverter( typeof( datetime_iso8601_converter ) )]
public System.DateTime created_utc;
My converter class is as follows:
public class datetime_iso8601_converter : Newtonsoft.Json.Converters.IsoDateTimeConverter
{
public datetime_iso8601_converter()
{
// Set format that all DateTime values will use ...
base.DateTimeFormat = "yyyy-MM-ddTHH:mm:ss.fffffff";
}
}
If I run a test using the debugger, for example:
created_utc = System.DateTime.MinValue;
I can see the following line is executed:
base.DateTimeFormat = "yyyy-MM-ddTHH:mm:ss.fffffff";
However, the resulting JSON date/time value that gets written is:
"0001-01-01T00:00:00"
SECOND ATTEMPT:
I tried the following converter ...
public class datetime_iso8601_converter : Newtonsoft.Json.Converters.DateTimeConverterBase
{
// The format that all datetime values will use ...
private const String k_fmt_datetime_iso8601 = "yyyy-MM-ddTHH:mm:ss.fffffff";
// Write the given datetime value using the format above ...
public override void WriteJson( JsonWriter writer, object value, JsonSerializer serializer )
{
if ( value is System.DateTime )
{
String dt_str;
System.DateTime dt;
dt = ( System.DateTime ) value;
dt_str = dt.ToString( k_fmt_datetime_iso8601 );
writer.WriteRawValue( dt_str );
}
else
{
throw new ArgumentException( "value is not System.DateTime" );
}
}
// Return a datetime value ...
public override object ReadJson( JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer )
{
if ( reader.TokenType != Newtonsoft.Json.JsonToken.Date )
{
throw new Exception( "Invalid token. Expected Date" );
}
return reader.Value;
}
}
Again using the debugger I can see that dt_str is set to a value of:
"0001-01-01T00:00:00.0000000"
but the value that actually gets written is:
"0001-01-01T00:00:00"
I do not understand why.
HOW can I get all date/time values saved in the format required?
Thanks in advance.

Answer 1

The above issue was present in an environment that was using Azure Functions. The current release of Azure functions 1.0.13 does not seem to support the binding redirects, i.e.:
[JsonConverter( typeof( datetime_iso8601_converter ) )]
However, release 1.22.0 will support JsonSettings and binding redirects (hopefully).

Answer 2

Just ran into the same thing. The solution to is to override Newtonsoft's time format string and have it use fffffff instead of FFFFFFF 🙂
See https://github.com/JamesNK/Newtonsoft.Json/issues/2780#issuecomment-1363704872 for sample code and details.