.NET 6项目Docker构建失败：COPY找不到Db项目文件的解决办法

你的项目结构如下：

TestProject
 - MyProject.sln
 - docker-compose.yaml
 - MyProject/
    - MyProject.csproj
    - Dockerfile
 - MyProject.Db/
     - MyProject.Db.csproj   

构建时出现错误：

ERROR  [app build 4/8] COPY [/MyProject.Db/MyProject.Db.csproj, MyProject.Db/]:
------
failed to solve: failed to compute cache key: failed to calculate checksum of ref 9dfeae07-144f-4a1a-9a88-4816eb08f9d9::p80g09cb0geba6x3tewswlfug: "/MyProject.Db/MyProject.Db.csproj": not found

问题根源：当前docker-compose.yaml中app服务的构建上下文设为./MyProject，导致Dockerfile执行时无法访问上层目录的MyProject.Db文件夹。

解决方案（无需移动Dockerfile） #

步骤1：修改docker-compose.yaml的app服务构建配置

将app服务的构建上下文改为项目根目录，并指定Dockerfile的完整路径：

version: '3.8'

services:
  database:
    build:
      context: ./MyProject.Db
      dockerfile: Dockerfile
    ports:
      - "1433:1433"

  app:
    build:
      context: .  # 改为项目根目录作为构建上下文
      dockerfile: MyProject/Dockerfile  # 指定Dockerfile的位置
    ports:
      - "8080:80"
    depends_on:
      - database

步骤2：调整Dockerfile中的COPY命令

由于构建上下文变为根目录，需要修改文件路径以正确复制项目文件：

# Stage 1: Base Image with ASP.NET runtime
FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443

# Stage 2: Build Image with SDK for compiling the application
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
# 从根上下文复制两个项目的csproj文件
COPY ["MyProject/MyProject.csproj", "MyProject/"]
COPY ["MyProject.Db/MyProject.Db.csproj", "MyProject.Db/"]

RUN dotnet restore "MyProject/MyProject.csproj"
WORKDIR "/src/MyProject"
# 只复制MyProject目录下的文件到当前工作目录
COPY ["MyProject/", "."]
RUN dotnet build "MyProject.csproj" -c Release -o /app/build

# Stage 3: Publish Image for a smaller runtime image
FROM build AS publish
RUN dotnet publish "MyProject.csproj" -c Release -o /app/publish /p:UseAppHost=false

# Stage 4: Final Image with only necessary artifacts
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "MyProject.dll"]

原理说明 #

• 将构建上下文改为项目根目录后，Docker可以访问所有子目录的文件，包括MyProject.Db。
• 调整COPY命令的路径，确保从根上下文正确复制所需文件，同时避免复制不必要的目录。

内容的提问来源于stack exchange，提问作者HC1122