Ubuntu下Docker无法启动Blazor项目问题求助

问题场景 #

在Ubuntu 24.04上用Rider 2025.1.3创建.NET 9 Blazor Server项目（默认带Counter/Weather页面，本地运行正常），使用Rider自动生成的Dockerfile构建镜像后，容器启动失败，报错：

The command could not be loaded, possibly because:

• You intended to execute a .NET application:
  The application 'SampleBlazor.dll' does not exist.
• You intended to execute a .NET SDK command:
  No .NET SDKs were found.

已禁用Rider的fast build功能，自动生成的Dockerfile如下：

FROM mcr.microsoft.com/dotnet/aspnet:9.0 AS base
USER $APP_UID
WORKDIR /app
EXPOSE 8080
EXPOSE 8081

FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["SampleBlazor/SampleBlazor.csproj", "SampleBlazor/"]
RUN dotnet restore "SampleBlazor/SampleBlazor.csproj"
COPY . .
WORKDIR "/src/SampleBlazor"
RUN dotnet build "./SampleBlazor.csproj" -c $BUILD_CONFIGURATION -o /app/build

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

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

解决步骤 #

1. 确认发布输出的程序集名称 #

本地执行发布命令，查看输出目录的文件：

dotnet publish -c Release

进入bin/Release/net9.0/publish目录，检查是否存在SampleBlazor.dll。若文件名有差异（比如带后缀或命名变化），同步修改Dockerfile中ENTRYPOINT的文件名。

2. 检查Docker构建上下文 #

执行docker build命令时，确保当前工作目录是项目根目录（即包含SampleBlazor子文件夹的目录），否则COPY步骤会找不到项目文件，导致发布不完整。

3. 排查权限问题 #

暂时注释掉USER $APP_UID行，测试是否因权限不足无法读取文件：

FROM mcr.microsoft.com/dotnet/aspnet:9.0 AS base
# USER $APP_UID
WORKDIR /app
EXPOSE 8080
EXPOSE 8081

若启动正常，再重新配置用户权限。

4. 验证发布阶段输出 #

在publish阶段添加查看命令，确认文件是否生成：

FROM build AS publish
ARG BUILD_CONFIGURATION=Release
RUN dotnet publish "./SampleBlazor.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false
# 验证发布文件
RUN ls -la /app/publish

构建时查看输出，确认SampleBlazor.dll存在于目标目录。

修正后的Dockerfile示例 #

FROM mcr.microsoft.com/dotnet/aspnet:9.0 AS base
WORKDIR /app
EXPOSE 8080
EXPOSE 8081

FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["SampleBlazor/SampleBlazor.csproj", "SampleBlazor/"]
RUN dotnet restore "SampleBlazor/SampleBlazor.csproj"
COPY . .
WORKDIR "/src/SampleBlazor"
RUN dotnet build "./SampleBlazor.csproj" -c $BUILD_CONFIGURATION -o /app/build

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

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

内容的提问来源于stack exchange，提问作者StefanG