Supported data types

.NET value	Column	Stored as
string	nvarchar(n), varchar(n), nchar(n), nvarchar(max)	as written (nchar(n) pads with spaces)
byte / short / int / long	tinyint / smallint / int / bigint	200 / 32000 / 2000000000 / 9000000000000
decimal	decimal(p, s), money	12345.678901
float / double	real / float	3.25 / 2.718281828459045
bool	bit	1
Guid	uniqueidentifier	6F9619FF-8B86-D011-B42D-00C04FC964FF
DateTimeOffset	datetimeoffset	the moment, in UTC: 22:30 +08:00 is stored as 2026-11-07 14:30:00 +00:00. The same with a hand-written catalog, a preload or none: like PostgreSQL and MySQL, ARX keeps the moment, not the offset (store the offset in a column of its own if the application needs it)
DateTimeOffset	datetime2, datetime	the moment in UTC (2026-11-07 14:30:00), with or without a catalog (SQL Server alone would drop the offset and keep 22:30, eight hours off)
DateTime	datetime2, datetime	as written: 2026-11-07 09:00:00 (datetime rounds to 1/300 of a second)
DateOnly / TimeOnly	date / time	2026-11-07 / 17:45:30
byte[], ArxBytea	varbinary(n), varbinary(max)	0xCAFE
ArxJsonB	nvarchar(max), with CHECK (ISJSON(column) = 1)	the JSON text (invalid JSON fails the check: ARX3004)
ArxEntityReference	the lookup column	the referenced id
ArxSelectionSetValue	the set's column	the option's code
null	any	NULL
sbyte / ushort / uint / ulong	converted to smallint / int / bigint / decimal	-100 / 65000 / 4000000000 / 18446744073709551615
char	text	X
a plain enum	refused (ARX1007)	write (int)value or value.ToString(), or use a selection set, which stores the code its set declares
DateTime with Kind Utc	datetimeoffset	the moment, offset +00:00
DateTime with Kind Local	datetime2, datetimeoffset	converted to UTC first

Refused before anything is sent: any other type (ARX1007 UnsupportedValueType: write uri.ToString() rather than a Uri); arrays (ARX8001: SQL Server has no array columns, so store a list as delimited text, JSON or rows of its own); NaN and the infinities, and a TimeSpan below zero or of 24 hours or more (ARX4001: time holds a time of day, so store a duration as a number).

With the column types preloaded (ArxPreLoadMode.DataTypes), a number with a fraction written to a whole-number column is refused before SQL Server (ARX4001 ValueOutOfRange) on a create, an update and a write by a filter, where SQL Server would round or truncate it; a condition in a read (qty < 7.5) isn't refused. A NaN or an infinity written to a declared decimal column is refused the same way.

SQL Server converts some values silently that other databases refuse: "42" into an int, a number into a bit, a decimal into an int by cutting off the fraction. A preload with column types (ArxPreLoadMode.DataTypes) refuses those before the database. RealCase2_EveryDataType writes every row of this table and prints what SQL Server stored.

You have	Use	Column
A moment (an order was placed)	DateTimeOffset	datetimeoffset
A moment, in a column without an offset	DateTime with Kind Utc	datetime2 (store UTC, read it back as UTC)
A wall-clock time with no zone	DateTime with Kind Unspecified	datetime2
A calendar date	DateOnly	date
A time of day	TimeOnly	time
A duration	a number (seconds, minutes)	int, bigint

SQL Server keeps no time zone: datetime2 stores the clock time it is given, and datetimeoffset the clock time and its offset. ARX writes a DateTimeOffset as its UTC instant and converts a local DateTime to UTC first, so a moment is never stored hours off. Refused: default(DateTime) (ARX1013: it means "not set", and SQL Server would store 0001-01-01; use null). ARX never parses a string as a date, but SQL Server converts one it can read, by the session's date format (01/07/1992 is January 7 under us_english), and refuses one it can't (ARX4003); with a schema preloaded with data types, ARX refuses every date string first (ARX4004). Parse dates yourself. Full rules: Data types.

SQL Server column	Reads back as	Notes
nvarchar(n), varchar(n), nchar(n), nvarchar(max)	string	nchar(n) keeps its padding spaces; "" stays ""
tinyint / smallint / int / bigint	byte / short / int / long
decimal(p, s), money	decimal	More than 28 significant digits: ARX4001 ValueOutOfRange
real / float	float / double
bit	bool
uniqueidentifier	Guid
datetimeoffset	DateTimeOffset	The clock time and the offset it was stored with
datetime2, datetime, smalldatetime	DateTime, Kind Unspecified	The clock time as stored: SQL Server keeps no zone
date / time	DateOnly / TimeOnly
varbinary(n), varbinary(max), rowversion	byte[]
JSON in nvarchar(max)	string	SQL Server 2022 has no JSON type: the text as stored
sql_variant	the value's own type
An alias type (CREATE TYPE … FROM nvarchar(320))	Its base type
A declared lookup (.Lookup(...))	ArxEntityReference	Name from the referenced table's .DisplayName(...)
A selection set column	Its stored code	entity.GetSelectionSet(column, set, catalog) gives the option
NULL	null	The attribute is present, with a null value

RealCase1_EveryDataTypeReadBack writes one row of every type with Create and prints each value's .NET type as it reads back.