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

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