UA-.NETStandard/Stack/Opc.Ua.Types/Encoders

OPC UA Encoders and Decoders

Json

Built-in Data Types

The following table lists the OPC UA built-in data types as defined in OPC UA Part 6 - Table 1, extended with the default JSON produced by JsonEncoder in Compact and Verbose mode (see JsonEncoderOptions).

The Nullable column indicates whether a null JSON value exists for the type. The Default column specifies the default value when one is needed; the default for all arrays is null.

In Compact mode (IgnoreNullValues=true, IgnoreDefaultValues=true) every default value is omitted — the field is not written to the output at all.

Id	Name	Nullable	Default	Description	Verbose	Compact
1	Boolean	No	false	A two-state logical value (true or false).	false	(omitted)
2	SByte	No	0	An integer value between −128 and 127.	0	(omitted)
3	Byte	No	0	An integer value between 0 and 255.	0	(omitted)
4	Int16	No	0	An integer value between −32 768 and 32 767.	0	(omitted)
5	UInt16	No	0	An integer value between 0 and 65 535.	0	(omitted)
6	Int32	No	0	An integer value between −2 147 483 648 and 2 147 483 647.	0	(omitted)
7	UInt32	No	0	An integer value between 0 and 4 294 967 295.	0	(omitted)
8	Int64	No	0	An integer value between −9.2e18 and 9.2e18.	"0"	(omitted)
9	UInt64	No	0	An integer value between 0 and 1.8e19.	"0"	(omitted)
10	Float	No	0	An IEEE single precision (32 bit) floating point value.	0	(omitted)
11	Double	No	0	An IEEE double precision (64 bit) floating point value.	0	(omitted)
12	String	Yes	null	A sequence of Unicode characters.	null	(omitted)
13	DateTime	Yes	MinValue	An instance in time.	null	(omitted)
14	Guid	Yes	All zeros	A 16-byte globally unique identifier.	null	(omitted)
15	ByteString	Yes	null	A sequence of octets.	null	(omitted)
16	XmlElement	Yes	null	A Unicode string that is an XML element.	null	(omitted)
17	NodeId	Yes	All default	An identifier for a node in the address space.	null	(omitted)
18	ExpandedNodeId	Yes	All default	A NodeId allowing a namespace URI instead of an index.	null	(omitted)
19	StatusCode	No	Good	A numeric identifier for an error or condition.	{}	(omitted)
20	QualifiedName	Yes	All default	A name qualified by a namespace.	null	(omitted)
21	LocalizedText	Yes	All default	Human readable text with an optional locale identifier.	null	(omitted)
22	ExtensionObject	Yes	All default	A structure with app-specific data that may not be recognized.	null	(omitted)
23	DataValue	Yes	All default	A data value with an associated status code and timestamps.	null	(omitted)
24	Variant	Yes	Null	A union of all of the types specified above.	null	(omitted)
25	DiagnosticInfo	Yes	No fields	Detailed error and diagnostic info associated with a StatusCode.	null	(omitted)

Notes

• All non-nullable types are encoded as their default value when they equal the default. In Compact mode, all default values are omitted.
  • Int64 / UInt64 are encoded as JSON strings (e.g. "0", "42") because JSON numbers cannot precisely represent the full 64-bit range.
  • StatusCode Good is encoded as an empty JSON object {} in Verbose mode. A non-Good StatusCode includes Code (UInt32) and, in Verbose mode only, a Symbol string (e.g. {"Code":2147483648,"Symbol":"Bad"}). Compact mode omits the Symbol.
  • DateTime is encoded as an ISO 8601 string (e.g. "2024-01-01T00:00:00Z"). DateTimeUtc.MinValue is treated as null.
  • Guid is encoded as a string (e.g. "72962B91-FA75-4AE6-8D28-B404DC7DAF63"). Guid.Empty is treated as null.
• All nullable types are encoded as null when they equal null. In Compact mode, all default values are omitted.
  • ByteString is encoded as a Base64 string.
  • XmlElement is encoded as a string containing the outer XML.
  • NodeId / ExpandedNodeId are encoded as formatted strings (e.g. "nsu=http://opcfoundation.org/UA/;i=2258").
  • QualifiedName is encoded as a formatted string (e.g. "nsu=http://opcfoundation.org/UA/;ServerStatus").
  • LocalizedText is encoded as a JSON object (e.g. {"Text":"Hello","Locale":"en"}).
  • Variant is encoded as a JSON object with UaType and Value (e.g. {"UaType":6,"Value":42}). In Compact mode, Value is omitted when it equals the type default.
  • DataValue is encoded like a Variant with additional StatusCode, SourceTimestamp, SourcePicoseconds, ServerTimestamp, and ServerPicoseconds fields (omitted when at their defaults).
  • ExtensionObject is encoded as a JSON object. Encodeable bodies are inlined with a UaTypeId field; binary/XML bodies use UaEncoding and UaBody fields.
  • DiagnosticInfo is encoded as a JSON object with optional fields SymbolicId, NamespaceUri, Locale, LocalizedText, AdditionalInfo, InnerStatusCode, and InnerDiagnosticInfo.