Replace legacy WebApi.Client multipart parsing with modern WebUtilities

[adrianiftode]

Removes the legacy Microsoft.AspNet.WebApi.Client package dependency and its high-allocation MultipartMemoryStreamProvider execution path.

• Replaces ReadAsMultipartAsync with an efficient custom extension utilizing MultipartReader from Microsoft.AspNetCore.WebUtilities.
• Safely isolates and eagerly buffers individual multipart section data into memory streams to prevent Unexpected end of Stream exceptions during asynchronous iterations.
• Preserves downstream HttpContent polymorphic formatting and streaming architectures across all multi-targeted platforms (netstandard2.0, net8.0, and net10.0).
• Keeps the modern .NET targets clear of unneeded dependencies by cleanly scoping legacy package assets to the .NET Standard target.

Before

λ dotnet list src/FluentAssertions.Web/FluentAssertions.Web.csproj package --include-transitive

Build succeeded in 3.6s
Restore complete (0.6s)

Build succeeded in 0.9s
Project 'FluentAssertions.Web' has the following package references
   [netstandard2.0]:
   Top-level Package             Requested       Resolved
   > FluentAssertions            [6.5.1,8.0.0)   6.5.1
   > NETStandard.Library   (A)   [2.0.3, )       2.0.3

   Transitive Package                            Resolved
   > Microsoft.AspNet.WebApi.Client              6.0.0
   > Microsoft.Bcl.AsyncInterfaces               8.0.0
   > Microsoft.NETCore.Platforms                 1.1.0
   > Newtonsoft.Json                             13.0.3
   > Newtonsoft.Json.Bson                        1.0.2
   > System.Buffers                              4.5.1
   > System.Memory                               4.5.5
   > System.Net.Http.Json                        8.0.1
   > System.Numerics.Vectors                     4.4.0
   > System.Runtime.CompilerServices.Unsafe      6.0.0
   > System.Text.Encodings.Web                   8.0.0
   > System.Text.Json                            8.0.5
   > System.Threading.Tasks.Extensions           4.5.4

(A) : Auto-referenced package.

After

λ dotnet list src/FluentAssertions.Web/FluentAssertions.Web.csproj package --include-transitive
Restore complete (0.7s)

Build succeeded in 1.2s
Project 'FluentAssertions.Web' has the following package references
   [netstandard2.0]:
   Top-level Package             Requested       Resolved
   > FluentAssertions            [6.5.1,8.0.0)   6.5.1
   > NETStandard.Library   (A)   [2.0.3, )       2.0.3

   Transitive Package                            Resolved
   > Microsoft.AspNetCore.WebUtilities           2.3.0
   > Microsoft.Bcl.AsyncInterfaces               8.0.0
   > Microsoft.Extensions.Primitives             8.0.0
   > Microsoft.Net.Http.Headers                  2.3.0
   > Microsoft.NETCore.Platforms                 1.1.0
   > System.Buffers                              4.6.0
   > System.Memory                               4.5.5
   > System.Net.Http.Json                        8.0.1
   > System.Numerics.Vectors                     4.4.0
   > System.Runtime.CompilerServices.Unsafe      6.0.0
   > System.Text.Encodings.Web                   8.0.0
   > System.Text.Json                            8.0.5
   > System.Threading.Tasks.Extensions           4.5.4

[jetersen]

Thanks! That's an even cleaner solution then my PR 😅

[adrianiftode]

Yeah, I remembered about this issue, and with some AI I could implement that multi part reader. At the time of your PR I thought it was still a difficult task, but yeah, times have changed.

…

On Tue, Jul 28, 2026 at 6:22 PM Joseph Petersen ***@***.***> wrote: *jetersen* left a comment (adrianiftode/FluentAssertions.Web#156) <#156 (comment)> Thanks! That's an even cleaner solution then my PR 😅 — Reply to this email directly, view it on GitHub <#156?email_source=notifications&email_token=ADI5U23KZ5R2TX2EZ5VIPLD5HDOODA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKMJQG42DINZVGQ32M4TFMFZW63VMON2GC5DFL5RWQYLOM5S2KZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-5107447547>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADI5U2YYLLVJLC6N7DUVNFL5HDOODAVCNFSNUABFKJSXA33TNF2G64TZHMZDAOBRGIZTQNJTHNEXG43VMU5TIOJZG4YDCNJRGQ2KC5QC> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/ADI5U254IT6EUJB47P4MUKT5HDOODA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKMJQG42DINZVGQ32M4TFMFZW63VMON2GC5DFL5RWQYLOM5S2KZLWMVXHJKTGN5XXIZLSL5UW64Y> and Android <https://github.com/notifications/mobile/android/ADI5U25E7UR45H3LQQNDQND5HDOODA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKMJQG42DINZVGQ32M4TFMFZW63VMON2GC5DFL5RWQYLOM5S2KZLWMVXHJLTGN5XXIZLSL5QW4ZDSN5UWI>. Download it today! You are receiving this because you modified the open/close state.Message ID: ***@***.***>