.NET 7 Blazor Server启用Razor源生成器时路由错误求助

问题背景 #

• 环境：.NET SDK 7.0.305 x64 + 6.0.411 x64，基于Blazor Server模板创建，启用Docker、禁用HTTPS，解决方案与项目同目录
• 现象：
  • 设置<UseRazorSourceGenerator>false</UseRazorSourceGenerator>：应用正常加载，但热重载失效
  • 设置<UseRazorSourceGenerator>true</UseRazorSourceGenerator>：启动抛出错误：

    InvalidOperationException: Cannot find the fallback endpoint specified by route values: { page: /_Host, area: }
    

    完整堆栈跟踪：

    Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure.DynamicPageEndpointMatcherPolicy.ApplyAsync(HttpContext httpContext, CandidateSet candidates)
    Microsoft.AspNetCore.Routing.Matching.DfaMatcher.SelectEndpointWithPoliciesAsync(HttpContext httpContext, IEndpointSelectorPolicy[] policies, CandidateSet candidateSet)
    Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.<Invoke>g__AwaitMatch|8_1(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task matchTask)
    Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
    Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
    Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)
    

• 已排查：_Host.cshtml未移出Pages文件夹，尝试过Startup.cs相关方案无效

解决方案 #

1. 修正项目文件的Razor配置 #

确保项目文件中包含正确的Razor源生成器及Razor Pages依赖配置：

<PropertyGroup>
  <TargetFramework>net7.0</TargetFramework>
  <Nullable>enable</Nullable>
  <ImplicitUsings>enable</ImplicitUsings>
  <UseRazorSourceGenerator>true</UseRazorSourceGenerator>
</PropertyGroup>

<ItemGroup>
  <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="7.0.10" />
  <PackageReference Include="Microsoft.AspNetCore.Mvc.RazorPages" Version="7.0.10" />
</ItemGroup>

2. 验证Program.cs端点映射顺序 #

对于.NET7的顶级Program.cs，必须保证Razor Pages端点映射在Blazor fallback之前，且配置完整：

var builder = WebApplication.CreateBuilder(args);

// 注册Razor Pages和Blazor服务
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();

var app = builder.Build();

if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
}
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();

// 先映射Razor Pages端点
app.MapRazorPages();
// 再映射Blazor Hub和fallback到_Host
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");

app.Run();

注意：MapRazorPages()必须在MapFallbackToPage("/_Host")之前执行，否则Razor Pages路由无法被正确识别。

3. 清理重建项目 #

• 删除项目根目录下的bin、obj文件夹
• 清理NuGet缓存：执行命令 dotnet nuget locals all --clear
• 重新生成项目：dotnet build

4. 检查Docker配置（若启用Docker） #

确保Dockerfile中完整复制了项目文件，尤其是Pages目录下的_Host.cshtml：

FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
WORKDIR /src
COPY ["YourProjectName.csproj", "."]
RUN dotnet restore "./YourProjectName.csproj"
# 复制所有项目文件，包括Pages目录
COPY . .
WORKDIR "/src/."
RUN dotnet build "YourProjectName.csproj" -c Release -o /app/build

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

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

避免因Docker构建时遗漏Razor文件导致的路由问题。

5. 指定SDK运行时版本 #

在项目文件中明确指定.NET7的运行时版本，避免多SDK版本冲突：

<PropertyGroup>
  <TargetFramework>net7.0</TargetFramework>
  <Nullable>enable</Nullable>
  <ImplicitUsings>enable</ImplicitUsings>
  <UseRazorSourceGenerator>true</UseRazorSourceGenerator>
  <RuntimeFrameworkVersion>7.0.10</RuntimeFrameworkVersion>
</PropertyGroup>

内容的提问来源于stack exchange，提问作者MST