Blazor Web 应用如何实现Auto模式

本文介绍Blazor Web应用Auto交互呈现模式的实现方案，如下示例是基于 Known 框架来实现的，该解决方案共有3个项目，具体实现步骤如下：

1. 前后端共用项目

• 创建前后端共用类库项目Sample，定义系统的实体类、数据模型、服务接口、常量、枚举等，项目工程文件内容如下：

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
    </PropertyGroup>
</Project>

• 在该项目中添加示例服务接口，继承框架IService

//IService为框架定义的Api服务接口，用于标识该接口为前后端交互接口
//程序启动时，框架自动查找Assembly中的接口，根据接口定义WebApi路由
//该示例路由为：/Test/GetMessage
public interface ITestService : IService {
    Task<string> GetMessageAsync();
}

2. 客户端项目

• 创建客户端项目Sample.Client，引用WebAssembly所需依赖，引用Castle依赖动态代理Http请求后端WebApi，项目工程文件内容如下：

<Project Sdk="Microsoft.NET.Sdk.BlazorWebAssembly">
    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <NoDefaultLaunchSettingsFile>true</NoDefaultLaunchSettingsFile>
        <StaticWebAssetProjectMode>Default</StaticWebAssetProjectMode>
    </PropertyGroup>
    <ItemGroup>
        <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="8.0.6" />
        <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Authentication" Version="8.0.6" />
        <PackageReference Include="Microsoft.Extensions.Http" Version="8.0.0" />
        <PackageReference Include="Castle.Core" Version="5.1.1" />
        <PackageReference Include="Castle.Core.AsyncInterceptor" Version="2.1.0" />
        <ProjectReference Include="..\Sample\Sample.csproj" />
    </ItemGroup>
</Project>

• 添加拦截器HttpClientInterceptor.cs类文件，继承Castle.DynamicProxy.IAsyncInterceptor，实现Http动态代理

using Castle.DynamicProxy;

namespace Sample.Client;

// HttpInterceptor为框架封装的拦截器
public class HttpClientInterceptor<T>(IServiceScopeFactory provider) : HttpInterceptor<T>(provider), IAsyncInterceptor where T : class {
    protected override async Task<HttpClient> CreateClientAsync() {
        var type = typeof(T);
        var factory = await ServiceFactory.CreateAsync<IHttpClientFactory>();
        var client = factory.CreateClient(type.Name);
        client.BaseAddress = new Uri(Config.HostUrl);
        return client;
    }

    public void InterceptAsynchronous(IInvocation invocation) {
        invocation.ReturnValue = SendAsync(invocation.Method, invocation.Arguments);
    }

    public void InterceptAsynchronous<TResult>(IInvocation invocation) {
        invocation.ReturnValue = SendAsync<TResult>(invocation.Method, invocation.Arguments);
    }

    public void InterceptSynchronous(IInvocation invocation) { }
}

• 在Program.cs文件中添加客户端配置

//使用Castle代理生成器创建Http代理类型
private static readonly ProxyGenerator Generator = new();

services.AddHttpClient();
//添加KnownClient，注入拦截器提供者
services.AddKnownClient(info =>
{
    info.InterceptorType = type => typeof(HttpClientInterceptor<>).MakeGenericType(type);
    info.InterceptorProvider = (type, interceptor) =>
    {
        return Generator.CreateInterfaceProxyWithoutTarget(type, ((IAsyncInterceptor)interceptor).ToInterceptor());
    };
});

• 添加测试页面组件Test.razor

@page "/test"

<h1>@message</h1>

@code {
    //注入服务与Server模式注入没有区别
    [Inject] private ITestService Service { get; set; }
    private string message;
    
    protected override async Task OnAfterRenderAsync(bool firstRender) {
        await base.OnAfterRenderAsync(firstRender);
        if (firstRender)
            message = await Service.GetMessageAsync();
        //这里的Service实例，会根据渲染模式自动切换
        //SSR时，就是后端实现ITestService的实现类的实例
        //CSR时，就是Castle代理生成器创建的代理类的实例
    }
}

3. 服务端项目

• 创建服务端项目Sample.Web，项目工程文件内容如下：

<Project Sdk="Microsoft.NET.Sdk.Web">
    <PropertyGroup>
        <TargetFramework>net8.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
    </PropertyGroup>
    <ItemGroup>
        <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="8.0.6" />
        <ProjectReference Include="..\Sample.Client\Sample.Client.csproj" />
    </ItemGroup>
</Project>

• 修改App.razor文件中的呈现模式

<Routes @rendermode="InteractiveMode" />

@code {
    private InteractiveAutoRenderMode InteractiveMode => new(false);
}

• 添加TestService.cs实现服务接口

class  TestService : ITestService {
    public Task<string> GetMessageAsync() => Task.FromResult("test");
}

• 在Program.cs文件中添加服务端配置

//添加Known框架后端Core
services.AddKnownCore();
//添加Known框架自动生成WebApi
services.AddKnownWebApi();
//注入服务接口
services.AddScoped<ITestService, TestService>();

//使用Known框架静态文件和WebApi
app.UseKnown();

4. 结语

本文示例代码仅作Auto模式实现方案的参考，具体功能实现，可查看 Known 框架的实例源码。