If I create ASP.NET Core Web App (Razor Pages or Web API) with Docker then I get Dockerfile:

FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS base
USER app
WORKDIR /app
EXPOSE 8080

FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["WebApplication5/WebApplication5.csproj", "WebApplication5/"]
RUN dotnet restore "./WebApplication5/WebApplication5.csproj"
COPY . .
WORKDIR "/src/WebApplication5"
RUN dotnet build "./WebApplication5.csproj" -c $BUILD_CONFIGURATION -o /app/build

FROM build AS publish
ARG BUILD_CONFIGURATION=Release
RUN dotnet publish "./WebApplication5.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "WebApplication5.dll"]

The Dockerfile be in the same place where is “csproj”:

Now if I create pipeline (I choose “Deploy to Azure Kubernetes Service”) in Azure DevOps:

I get the pipeline:

trigger:
- master

resources:
- repo: self

variables:

  # Container registry service connection established during pipeline creation
  dockerRegistryServiceConnection: 'b9242279-99b2-45f6-8096-ea3190c4f6ed'
  imageRepository: 'xxx'
  containerRegistry: 'xxx.azurecr.io'
  dockerfilePath: '**/Dockerfile'
  tag: '$(Build.BuildId)'
  imagePullSecret: 'xxx-auth'

  # Agent VM image name
  vmImageName: 'ubuntu-latest'


stages:
- stage: Build
  displayName: Build stage
  jobs:
  - job: Build
    displayName: Build
    pool:
      vmImage: $(vmImageName)
    steps:
    - task: Docker@2
      displayName: Build and push an image to container registry
      inputs:
        command: buildAndPush
        repository: $(imageRepository)
        dockerfile: $(dockerfilePath)
        containerRegistry: $(dockerRegistryServiceConnection)
        tags: |
          $(tag)

    - upload: manifests
      artifact: manifests

- stage: Deploy
  displayName: Deploy stage
  dependsOn: Build

  jobs:
  - deployment: Deploy
    displayName: Deploy
    pool:
      vmImage: $(vmImageName)
    environment: 'xxx.default'
    strategy:
      runOnce:
        deploy:
          steps:
          - task: KubernetesManifest@0
            displayName: Create imagePullSecret
            inputs:
              action: createSecret
              secretName: $(imagePullSecret)
              dockerRegistryEndpoint: $(dockerRegistryServiceConnection)

          - task: KubernetesManifest@0
            displayName: Deploy to Kubernetes cluster
            inputs:
              action: deploy
              manifests: |
                $(Pipeline.Workspace)/manifests/deployment.yml
                $(Pipeline.Workspace)/manifests/service.yml
              imagePullSecrets: |
                $(imagePullSecret)
              containers: |
                $(containerRegistry)/$(imageRepository):$(tag)

As a result when I try to deploy that application using the Azure pipelines I get the error:

##[error]Dockerfile:11
##[error]--------------------
##[error]   9 |     ARG BUILD_CONFIGURATION=Release
##[error]  10 |     WORKDIR /src
##[error]  11 | >>> COPY ["WebApplication5/WebApplication5.csproj", "WebApplication5/"]
##[error]  12 |     RUN dotnet restore "./WebApplication5/WebApplication5.csproj"
##[error]  13 |     COPY . .
##[error]--------------------
##[error]ERROR: failed to solve: failed to compute cache key: failed to calculate checksum of ref c314f485-2f42-4ab2-8fcd-b39be4f6283c::vv9n5bzxz7yeebiyzmmvn6nk7: "/WebApplication5/WebApplication5.csproj": not found
##[error]The process '/usr/bin/docker' failed with exit code 1

BUT if I move Dockerfile above and place it in the same place where is “csproj”:

then I deploy my application successfully but I cannot run my application locally because I have the error:

No Dockerfile could be found. Please make sure you have a Dockerfile called 'Dockerfile' adjacent to the project file.