What is the recommended way to store DateTimeOffsets to 'timestamp with time zone' fields and to avoid the exception: Cannot write DateTimeOffset with Offset=01:00:00 to PostgreSQL type 'timestamp with time zone'

Steps to reproduce

Just try to write any DateTimeOffset to a Postgres database using Dapper.

The issue

The DateTimeOffset value is not stored and the mapper throws an exception:

Exception message: Cannot write DateTimeOffset with Offset=01:00:00 to PostgreSQL type 'timestamp with time zone', only offset 0 (UTC) is supported. Note that it's not possible to mix DateTimes with different Kinds in an array/range. See the Npgsql.EnableLegacyTimestampBehavior AppContext switch to enable legacy behavior.
Stack trace: System.InvalidCastException: Cannot write DateTimeOffset with Offset=01:00:00 to PostgreSQL type 'timestamp with time zone', only offset 0 (UTC) is supported. Note that it's not possible to mix DateTimes with different Kinds in an array/range. See the Npgsql.EnableLegacyTimestampBehavior AppContext switch to enable legacy behavior.
   at Npgsql.Internal.TypeHandlers.DateTimeHandlers.TimestampTzHandler.ValidateAndGetLength(DateTimeOffset value, NpgsqlParameter parameter)
   at Npgsql.Internal.TypeHandlers.DateTimeHandlers.TimestampTzHandler.ValidateObjectAndGetLength(Object value, NpgsqlLengthCache& lengthCache, NpgsqlParameter parameter)
   at Npgsql.NpgsqlParameter.ValidateAndGetLength()
   at Npgsql.NpgsqlParameterCollection.ValidateAndBind(ConnectorTypeMapper typeMapper)
   at Npgsql.NpgsqlCommand.ExecuteReader(CommandBehavior behavior, Boolean async, CancellationToken cancellationToken)
   at Npgsql.NpgsqlCommand.ExecuteReader(CommandBehavior behavior, Boolean async, CancellationToken cancellationToken)
   at Npgsql.NpgsqlCommand.ExecuteNonQuery(Boolean async, CancellationToken cancellationToken)
   at Dapper.SqlMapper.ExecuteImplAsync(IDbConnection cnn, CommandDefinition command, Object param) in /_/Dapper/SqlMapper.Async.cs:line 654

Further technical details

Npgsql version: 6.0.0 PostgreSQL version: 13.0 Operating system: Windows 10 / Debian on Docker Dapper version: 2.0.123

Other details about my project setup: Nothing relevant, projects are running in the GMT+1 (In summer time GMT+2) and a German environment.

What is the preferred way to fix this issue? The only two things I can think of is:

• Set the Npgsql.EnableLegacyTimestampBehavior AppContext switch (Which will probably soon be removed, so updates are not possible anymore for me)
• Change all DateTimeOffsets manually to UTC and write them to the database (Not possible at all as this would take ages to check)
• Some kind of global “mapper” to change all DateTimeOffsets to UTC (No idea how this would work)

While I totally agree to @roji (https://www.roji.org/postgresql-dotnet-timestamp-mapping) that the naming of timestamptz in PostgreSQL is just bullshit to be honest, it would be nice to have a more generic solution (As I said, it’s possible to upgrade all my database calls, but I don’t want to do that as it takes ages…). Maybe, I’m wrong here and the Dapper people do have a solution I didn’t see yet.

[ghost]

For everyone running into the same questions. We “solved” it with EF core 6.0 by using a value converter for DateTimeOffset.

Bulk-configuring a value converter was recently introduced to EF core which we are taking advantage of. https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions?tabs=data-annotations#bulk-configuring-a-value-converter

public class DateTimeOffsetConverter : ValueConverter<DateTimeOffset, DateTimeOffset>
{
    public DateTimeOffsetConverter()
        : base(
            d => d.ToUniversalTime(),
            d => d.ToUniversalTime())
    {
    }
}

Overwrite in your DbContext

protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
{
    configurationBuilder
        .Properties<DateTimeOffset>()
        .HaveConversion<DateTimeOffsetConverter>();
}

[SeppPenner]

For everyone running into the same questions. We “solved” it with EF core 6.0 by using a value converter for DateTimeOffset.

Bulk-configuring a value converter was recently introduced to EF core which we are taking advantage of. https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions?tabs=data-annotations#bulk-configuring-a-value-converter

public class DateTimeOffsetConverter : ValueConverter<DateTimeOffset, DateTimeOffset>
{
    public DateTimeOffsetConverter()
        : base(
            d => d.ToUniversalTime(),
            d => d.ToUniversalTime())
    {
    }
}

Overwrite in your DbContext

protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
{
    configurationBuilder
        .Properties<DateTimeOffset>()
        .HaveConversion<DateTimeOffsetConverter>();
}

Nice. Sadly, I use Dapper and still didn’t have time to find the issue…