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Learn how to effectively suppress null properties during XML serialization in ASP.NET Web API using the correct serializer settings.
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This video is based on the question https://stackoverflow.com/q/67831439/ asked by the user 'Yossi G.' ( https://stackoverflow.com/u/9479959/ ) and on the answer https://stackoverflow.com/a/67861018/ provided by the user 'Yossi G.' ( https://stackoverflow.com/u/9479959/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Suppress null Values in XML Serialization with ASP.NET Web API

When working with ASP.NET Web API, developers often encounter issues related to XML serialization, particularly with how null values are handled. If you've ever tried to suppress null properties in your serialized XML and found it challenging, you're not alone. In this post, we'll walk through the common problems encountered when using the default XML serializer and how to resolve them effectively.

Understanding the Problem

In a recent case, a developer shared their experience about trying to suppress null properties from XML serialization in a simple class. They had declared some properties with the XmlElement(IsNullable = false) attribute and attempted to implement the ShouldSerialize pattern. However, despite their efforts, the XML output still included null properties, which is not the desired behavior.

Example Class

Here’s a simplified version of the class causing the issue:

[[See Video to Reveal this Text or Code Snippet]]

The Resulting XML

Instead of filtering out the null values, the generated XML still included tags for properties with null values:

[[See Video to Reveal this Text or Code Snippet]]

The Solution: Using XmlSerializer Explicitly

The root of the issue is that the attributes and methods applied for suppression of null values are only effective with the XmlSerializer, not the default DataContractSerializer used in ASP.NET Web API. To resolve the problem, you need to explicitly configure your Web API to use the XmlSerializer. Here’s how to do it:

Step-by-Step Configuration

Modify WebApiConfig Class: Locate your WebApiConfig class where you set up your API configuration.

Set the XML Formatter: Add the following line to specify the usage of XmlSerializer instead of the default serializer. Here is an example of the configuration method:

[[See Video to Reveal this Text or Code Snippet]]

Rebuild and Test: Rebuild your project and make a request to check if null values are properly suppressed in the resulting XML response.

Additional Considerations

While the above solution addresses the immediate problem, it raises two additional questions:

What is the default WebAPI Xml Serializer?
The default serializer used by WebAPI is the DataContractSerializer. It's different from the XmlSerializer, which offers more flexibility in handling XML attributes and tags.

Will the XML Structure Change Affect Deserialization?
Yes, the structure of XML emitted by both serializers can differ. Ensure that your receiving end is compatible with the XML format produced by the XmlSerializer to avoid deserialization issues.

Conclusion

Suppressing null values during XML serialization in ASP.NET Web API can be straightforward once you configure the serializer correctly. By switching to XmlSerializer, you can easily control the serialization behavior and avoid unwanted null elements in your XML output.

If you’re facing similar issues, adopt this method into your web API configuration and enjoy a cleaner, more efficient XML response. Happy coding!