Supported collection types in System.Text.Json

• 02/01/2021
• 4 minutes to read
• • t

This article gives an overview of which collections are supported for serialization and deserialization. System.Text.Json.JsonSerializer supports a collection type for serialization if it:

• Derives from IEnumerable.
• Contains elements that are serializable.

The serializer calls the GetEnumerator() method, and writes the elements.

Deserialization is more complicated and is not supported for some collection types.

The following sections are organized by namespace and show which types are supported for serialization and deserialization.

System.Array namespace

System.Collections namespace

System.Collections.Generic namespace

* See Supported key types.

System.Collections.Immutable namespace

* See Support round trip for Stack<T>.

** See Supported key types.

System.Collections.Specialized namespace

* When BitVector32 is deserialized, the Data property is skipped because it doesn't have a public setter. No exception is thrown.

System.Collections.Concurrent namespace

* See Support round trip for Stack<T>.

** See Supported key types.

System.Collections.ObjectModel namespace

Custom collections

Any collection type that isn't in one of the preceding namespaces is considered a custom collection. Such types include user-defined types and types defined by ASP.NET Core. For example, Microsoft.Extensions.Primitives is in this group.

All custom collections (everything that derives from IEnumerable) are supported for serialization, as long as their element types are supported.

Custom collections with deserialization support

A custom collection is supported for deserialization if it:

* See Support round trip for Stack<T>.

** See Supported key types.

Custom collections with known issues

There are known issues with the following custom collections:

• ExpandoObject: See dotnet/runtime#29690.
• DynamicObject: See dotnet/runtime#1808.
• DataTable: See dotnet/docs#21366.
• Microsoft.AspNetCore.Http.FormFile: See dotnet/runtime#1559.
• Microsoft.AspNetCore.Http.IFormCollection: See dotnet/runtime#1559.

For more information about known issues, see the open issues in System.Text.Json.

Supported key types

See also

• System.Text.Json overview
• Instantiate JsonSerializerOptions instances
• Enable case-insensitive matching
• Customize property names and values
• Ignore properties
• Allow invalid JSON
• Handle overflow JSON
• Preserve references
• Immutable types and non-public accessors
• Polymorphic serialization
• Migrate from Newtonsoft.Json to System.Text.Json
• Customize character encoding
• Write custom serializers and deserializers
• Write custom converters for JSON serialization
• DateTime and DateTimeOffset support
• System.Text.Json API reference
• System.Text.Json.Serialization API reference