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System.Text.Json now supports serializing and deserializing of IAsyncEnumerable<T> instances.
Previous behavior
In previous versions, System.Text.Json serialized IAsyncEnumerable<T> instances as empty JSON objects ({}). Deserialization failed with a JsonException.
New behavior
Asynchronous serialization methods now enumerate any IAsyncEnumerable<T> instances in an object graph and then serialize them as JSON arrays. Synchronous serializations methods do not support IAsyncEnumerable<T> serialization and throw a NotSupportedException.
Version introduced
.NET 6
Type of breaking change
This change can affect source compatibility. If you retarget to .NET 6, you won't get any compile-time errors, but you may encounter run-time serialization behavior differences.
Reason for change
This change was introduced to add support for streaming IAsyncEnumerable<T> responses in ASP.NET Core MVC.
Recommended action
Check if your serialization models contain types that implement IAsyncEnumerable<T> and determine if emitting the enumeration in the JSON output is desirable. You can disable IAsyncEnumerable<T> serialization in one of the following ways:
- Attach a JsonIgnoreAttribute to the property containing the IAsyncEnumerable<T>.
- Define a custom converter factory that serializes IAsyncEnumerable<T> instances as empty JSON objects.
Affected APIs
See also
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