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Use GetUtf8Bytes for remaining C# JSON deserialization paths - #11951

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Use GetUtf8Bytes for remaining C# JSON deserialization paths#11951
JoshLove-msft with Copilot wants to merge 2 commits into
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copilot/generated-serialization-improvement

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Copilot AI commented Sep 11, 2026 •
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Raw-JSON deserialization still round-trips UTF-8 through a UTF-16 string in several paths. Reusing GetUtf8Bytes() avoids that transcoding on .NET 9+ via JsonMarshal.GetRawUtf8Value.

  • Deserialization: Extend the helper already used for nested models to raw BinaryData, byte[], Stream, and BinaryData collection values.
  • Compatibility: Preserve Base64 decoding, null handling, and the older-framework fallback.
  • Coverage: Update generated baselines and cover UTF-8 fidelity, document disposal, and invalid elements.
// Before
data = BinaryData.FromString(prop.Value.GetRawText());

// After
data = prop.Value.GetUtf8Bytes();

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Copilot AI linked an issue Sep 11, 2026 that may be closed by this pull request
Generated serialization should use JsonMarshal.GetRawUtf8Value extension for better perf on net9.0+ #10766
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perf(http-client-csharp): use raw UTF-8 helper throughout JSON deseri…
0963e8c 
…alization

Co-authored-by: JoshLove-msft <54595583+JoshLove-msft@users.noreply.github.com>
@microsoft-github-policy-service microsoft-github-policy-service Bot added the emitter:client:csharp Issue for the C# client emitter: @typespec/http-client-csharp label Sep 11, 2026
Copilot AI changed the title [WIP] Enhance generated serialization using JsonMarshal.GetRawUtf8Value Use GetUtf8Bytes for remaining C# JSON deserialization paths Sep 11, 2026
Copilot AI requested a review from JoshLove-msft September 11, 2026 23:53
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JoshLove-msft marked this pull request as ready for review September 11, 2026 23:55
Copilot AI lite review requested due to automatic review settings September 11, 2026 23:55
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npm i https://pkg.pr.new/@typespec/http-client-csharp@11951

commit: 0963e8c

Copilot AI reviewed Sep 11, 2026
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🟢 Approval recommended

No unresolved blocking issues were identified.

Pull request overview

Updates C# JSON deserialization to preserve raw UTF-8 bytes and avoid unnecessary UTF-16 transcoding on .NET 9+.

Changes:

  • Uses GetUtf8Bytes() for raw BinaryData, byte arrays, streams, and collections.
  • Preserves Base64, null, and older-framework fallback behavior.
  • Adds UTF-8, disposal, and invalid-element coverage; refreshes generated baselines.
File summaries
File Summary
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Wrapper.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/UnknownPlant.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/UnknownPet.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/UnknownAnimal.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Tree.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Thing.Serialization.cs Updates raw union and property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/StreamingItem.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/RoundTripModel.Serialization.cs Updates raw and dictionary values.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ReturnsAnonymousModelResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/RenamedModelCustom.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/PageThing.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ModelWithRequiredNullableProperties.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ModelWithEmbeddedNonBodyParameters.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ListWithStringNextLinkResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ListWithNextLinkResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ListWithContinuationTokenResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/ListWithContinuationTokenHeaderResponseResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/GetWidgetMetricsResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/GetNotebookResponse.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Friend.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/DynamicModel.Serialization.cs Updates unknown-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local/Sample-TypeSpec/src/Generated/Models/Dog.Serialization.cs Updates raw-property deserialization.
packages/http-client-csharp/generator/TestProjects/Local.Tests/ModelSerializationExtensionsTests.cs Adds UTF-8 fidelity and lifecycle tests.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/TestData/ScmMethodProviderCollectionTests/ListOfValueTypeUsesJsonDoc(BinaryData).cs Updates collection baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/TestData/ScmMethodProviderCollectionTests/DictionaryOfValueTypeUsesJsonDoc(BinaryData).cs Updates dictionary baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/ReadOnlyMemPropertyType.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanReplaceSerializationMethod.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanPreserveArrayEncodingForCustomizedProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeSerializationMethodForRenamedProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeSerializationMethodForPropertyInBase.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeSerializationMethod.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizePropertyUsingField.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeLiteralExtensibleEnum(string,foo).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeLiteralExtensibleEnum(int32,1).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeExtensibleEnum(string).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeExtensibleEnum(int32).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeDeserializationMethodWithoutOptions.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanCustomizeDeserializationMethodWithOptions.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanChangePropertySerializedName.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanChangePropertyNameAndRedefineOriginal.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanChangePropertyName.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanChangeListOfEnumPropToListOfExtensibleEnum.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/SerializationCustomizationTests/CanChangeDictionaryToBinaryData.cs Updates raw binary deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/MrwSerializationTypeDefinitionTests/IsExactNamePropertySerializationUsesExactName(deserialize).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/MrwSerializationTypeDefinitionTests/IsExactNameModelSerializationUsesExactName.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/MrwSerializationTypeDefinitionTests/GetUtf8BytesIsUsedForMrwFallback.cs Updates fallback baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/DoesNotOverrideMethodsIfBaseTypeIsNotModel.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeUriProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeStringToFixedEnum.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizePropertyIntoReadOnlyMemory.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeNullableStringToFixedEnum.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeGuidProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeFixedEnumString.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeEnumToFrameworkType.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeEnumToFieldFrameworkType.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/ModelCustomizationTests/CanCustomizeBaseType.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DynamicModelSerializationTests/DeserializeModelWithBinaryDataAdditionalPropsBackCompat.cs Updates additional-property baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DynamicModelSerializationTests/DeserializeModelPropertyType.cs Updates raw property baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DiscriminatorTests/TestUnknownNestedDiscriminatorCastsToInterfaceType.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/TestDeserializationOfDurationMillisecondsIntegerWireType(Integer).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/TestDeserializationOfDurationMillisecondsIntegerWireType(Int64).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/TestDeserializationOfDurationMillisecondsIntegerWireType(Int32).cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/RequiredFileBinaryContentProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/OptionalFileBinaryContentProperty.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/DeserializationTests/DeserializeStruct.cs Updates generated deserialization baseline.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/MrwSerializationTypeDefinitionTests.cs Covers raw binary, byte-array, and stream paths.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/ScmMethodProviderCollection.cs Uses raw UTF-8 bytes for collection elements.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.cs Uses raw UTF-8 bytes for framework value deserialization.
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Generated serialization should use JsonMarshal.GetRawUtf8Value extension for better perf on net9.0+

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