Why docker build error on copy?

[ramalt]

I Have an example project like this:
.
├── HelloClasslib
│   ├── bin
│   ├── obj
│   └── HelloClasslib.csproj
└── HelloNet8
├── bin
├── obj
├── HelloNet8.csproj
└── Dockerfile

HelloNet8 Project references Helloclasslib and i stated this in Dockerfile like this:

COPY ../HelloClasslib/HelloClasslib.csproj /app/HelloClasslib/

But when I run the sudo docker build -t net8api-image -f Dockerfile . command, I get this error:

[+] Building 0.2s (12/12) FINISHED docker:default
=> [internal] load .dockerignore
=> => transferring context: 2B
=> [internal] load build definition from Dockerfile
=> => transferring dockerfile: 753B
=> [internal] load metadata for mcr.microsoft.com/dotnet/sdk:8.0
=> [build-env 1/6] FROM mcr.microsoft.com/dotnet/sdk:8.0
=> [internal] load build context
=> => transferring context: 3.96kB
=> CACHED [build-env 2/6] WORKDIR /app
=> CANCELED [build-env 3/6] COPY . ./
=> CACHED [build-env 4/6] RUN dotnet restore "./HelloNet8.csproj"
=> CACHED [build-env 5/6] RUN dotnet build "./HelloNet8.csproj" -c Release -o /app/build
=> CACHED [build-env 6/6] RUN dotnet publish -c Release -o out
=> CACHED [final-env 3/4] COPY --from=build-env /app/build/ .
=> ERROR [final-env 4/4] COPY ../Helloclasslib/Helloclasslib.csproj /app/Helloclasslib/

[final-env 4/4] COPY ../Helloclasslib/Helloclasslib.csproj /app/Helloclasslib/:

---

Dockerfile:25

23 | COPY --from=build-env /app/build/ .
24 |
25 | >>> COPY ../Helloclasslib/Helloclasslib.csproj /app/Helloclasslib/
26 |
27 | ENV ASPNETCORE_URLS=http://+:5073

ERROR: failed to solve: failed to compute cache key: failed to calculate checksum of ref c59727a0-f1ea-462f-809f-1ea468eef3bf::ke79s2mc58qbtixh8q4lynvyz: "/Helloclasslib/Helloclasslib.csproj": not found

I think this is related to docker context. I checked the file permissions:

[helloproject] ls -l
total 12
drwxrwxr-x 4 ram ram 4096 Ara 30 20:30 Helloclasslib
drwxrwxr-x 5 ram ram 4096 Ara 30 00:27 HelloNet8
-rw-rw-r-- 1 ram ram 1591 Ara 30 20:30 helloproject.sln
[helloproject] cd Helloclasslib
[Helloclasslib] ls -l
total 16
drwxrwxr-x 3 ram ram 4096 Ara 30 20:30 bin
-rw-rw-r-- 1 ram ram 147 Ara 30 20:49 Class1.cs
-r-xr--r-- 1 ram ram 218 Ara 30 20:29 Helloclasslib.csproj
drwxrwxr-x 3 ram ram 4096 Ara 30 20:30 obj

os: Ubuntu 22.04 jammy framework: .net 8 Docker version: 24.0.7, build afdd53b