Environment description

• .net 5
• asp.net core api
• windows 10、centos 7

dotnet --info
.NET SDK (反映任何 global.json):
 Version:   5.0.300
 Commit:    2e0c8c940e

运行时环境:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.300\

Host (useful for support):
  Version: 5.0.6
  Commit:  478b2f8c0e

.NET SDKs installed:
  5.0.300 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

Problem Description

There is a client which uses GB2312 character set encoding and uses https POST Content-Type:application/x-www-form-urlencoded; charset=GBK to call the API provided by me.
The data submitted by the client POST is encoded by System.Web.HttpUtility.UrlEncode("查重费用", Encoding.GetEncoding("gbk")); The encoded value is: %b2%e9%d6%d8%b7%d1%d3%c3.

The entire request message looks like this：

POST https://localhost:44334/api/test HTTP/1.1
User-Agent:Fiddler Everywhere
Content-Type:application/x-www-form-urlencoded; charset=GBK
Host:localhost:44334
Content-Length:27

su=%b2%e9%d6%d8%b7%d1%d3%c3

The value received by my API is indeed like this: %B2%E9%D6ط%D1%D3%C3.

The received code is like this:

// Program.cs
    public class Program
    {
        public static void Main(string[] args)
        {
            // The point of displaying this code is to tell you that the character set is registered.
            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);

            CreateHostBuilder(args).Build().Run();
        }
                ... omit other codes ...
    }

// TestController.cs
    [Route("api/[controller]")]
    [ApiController]
    public class TestController : ControllerBase
    {
        [HttpPost]
        public IActionResult Post()
        {
            // Here the correct value of Request.Form["su"] should be "查重费用", but it is actually  "%B2%E9%D6ط%D1%D3%C3"
            return Content(Request.Form["su"]);
        }
    }

I see asp.net core source code FormPipeReader.cs

        private string GetDecodedString(ReadOnlySpan<byte> readOnlySpan)
        {
            if (readOnlySpan.Length == 0)
            {
                return string.Empty;
            }
            else if (_encoding == Encoding.UTF8 || _encoding == Encoding.ASCII)
            {
                 ... omit other codes ...
            }
            else
            {
                // Slow path for Unicode and other encodings.
                // Just do raw string replacement.
                var decodedString = _encoding.GetString(readOnlySpan);
                decodedString = decodedString.Replace('+', ' ');
                return Uri.UnescapeDataString(decodedString);
            }
        }

If replace Uri.UnescapeDataString(decodedString) with System.Web.HttpUtility.UrlDecode(decodedString, _encoding), the problem I encountered can be solved.

Is it really correct to use Uri.UnescapeDataString(string) here?