AWS DynamoDB SDK support for .NET DateTimeOffset

The AWS DynamoDB SDK does not support the .NET DateTimeOffset datatype by default.

You may have received an exception similar to:

System.InvalidOperationException: Type System.Nullable System.DateTimeOffset is unsupported, it cannot be instantiated. at Amazon.DynamoDBv2.DataModel

But you can add a custom IPropertyConverter so that you can persist DateTimeOffset.

public class DateTimeOffsetPropertyConverter : IPropertyConverter

{

    public static readonly string DateTimeOffsetPersistenceFormatString = "yyyy-MM-ddTHH:mm:ss.ffffzzz";

    public object FromEntry(DynamoDBEntry entry)

    {

        if (entry == null)

        {

            throw new ArgumentNullException(nameof(entry));

        }

        var primitive = entry as Primitive;

        if (primitive == null)

        {

            throw new ArgumentException($"{nameof(entry)} [{entry?.GetType()?.Name}] is not an instance of {nameof(Primitive)}.");

        }

        var dateString = primitive.Value as string;

        if (string.IsNullOrWhiteSpace(dateString))

        {

            throw new ArgumentException($"{nameof(entry)} does not contain a string primitive value.");

        }

        if (DateTimeOffset.TryParse(dateString, out var dateTimeOffset))

        {

            return dateTimeOffset;

        }

        throw new ArgumentException($"{nameof(entry)} primitive string value could not be parsed.");

    }

    public DynamoDBEntry ToEntry(object value)

    {

        if (value == null)

        {

            throw new ArgumentNullException(nameof(value));

        }

        if (value is not DateTimeOffset)

        {

            throw new ArgumentException($"{nameof(value)} [{value.GetType().Name}] is not an instance of {nameof(DateTimeOffset)}.");

        }

        var dateTimeOffset = (DateTimeOffset)value;

        var entry = new Primitive(dateTimeOffset.ToString(DateTimeOffsetPersistenceFormatString));

        return entry;

    }

}

Hope this helps,
Aaron