Update the README and the CHANGELOG for the new UseNullText feature

Author: 0xced

CHANGELOG.md

@@ -4,6 +4,26 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.4.0][1.4.0] - 2025-09-19
+
+- Properties whose values are `null` are now always serialized with a `value` attribute. Thanks to @southernprogrammer for reporting this issue. See the [Null text](https://github.com/serilog-contrib/serilog-formatting-log4net#null-text) documentation in the README for more information.
+
+Before (1.3.1)
+
+```xml
+<log4net:properties>
+  <log4net:data name="key" />
+</log4net:properties>
+```
+
+After (1.4.0)
+
+```xml
+<log4net:properties>
+  <log4net:data name="key" value="(null)" />
+</log4net:properties>
+```
+
 ## [1.3.1][1.3.1] - 2025-04-30
 
 - Log events coming from `Microsoft.Extensions.Logging` are now identified if they have **either** an `EventId.Id` or an `EventId.Name` property. Previously, log events coming from `Microsoft.Extensions.Logging` were identified if they had **both** an `Id` and a `Name` property.
@@ -139,7 +159,8 @@ Still trying to figure out how to make everything fit together with [MinVer](htt
 
 - Implement log4j compatibility mode.
 
-[Unreleased]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.3.1...HEAD
+[Unreleased]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.4.0...HEAD
+[1.4.0]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.3.1...1.4.0
 [1.3.1]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.3.0...1.3.1
 [1.3.0]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.2.0...1.3.0
 [1.2.0]: https://github.com/serilog-contrib/serilog-formatting-log4net/compare/1.1.0...1.2.0

README.md

@@ -106,6 +106,28 @@ By default, Log4NetTextFormatter writes all messages and exceptions with a [CDAT
 new Log4NetTextFormatter(c => c.UseCDataMode(CDataMode.Never))
 ```
 
+### Null text
+
+Available since version 1.4.0
+
+By default, when a property value is `null`, the text used for its representation is `(null)`. This can be changed with the `UseNullText()` configuration method.
+
+Here's how to configure the formatter to use `🔷null🔷` when a property value is `null`.
+
+```c#
+new Log4NetTextFormatter(c => c.UseNullText("🔷null🔷"));
+```
+
+This will produce the following output.
+
+```xml
+<log4net:properties>
+  <log4net:data name="key" value="🔷null🔷" />
+</log4net:properties>
+```
+
+To restore compatibility with version 1.3.1 and earlier (which produced a non-compatible XML), `UseNullText(null)` can be called.
+
 ### XML Namespace
 
 You can remove the `log4net` XML namespace by calling `UseNoXmlNamespace()` on the options builder. This is useful if you want to spare some bytes and your log reader supports log4net XML events without namespace, like [Log4View](https://www.log4view.com) does.