如何在.NET 6中使用Razor渲染器？迁移后功能异常求解

方案一：配置RazorLight导入系统命名空间 #

RazorLight默认未导入常用系统命名空间，手动添加后即可使用Convert、Math等方法：

1. 安装RazorLight NuGet包
2. 初始化引擎时添加默认命名空间：

var engine = new RazorLightEngineBuilder()
    .UseMemoryCachingProvider()
    .AddDefaultNamespaces("System")
    .AddDefaultNamespaces("System.Globalization")
    .Build();

3. 渲染外部HTML字符串：

// 外部传入的带Razor语法的HTML
string externalHtml = "<p>金额：@Math.Round(Convert.ToDecimal(Model.Amount), 2) 元</p>";
var model = new { Amount = 99.987 };

// 编译并渲染
string renderedHtml = await engine.CompileRenderStringAsync("unique_template_key", externalHtml, model);

方案二：使用.NET官方Razor运行时编译服务 #

官方的Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation兼容性更好，原生支持所有系统类：

1. 安装NuGet包：Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation
2. 在Program.cs注册服务：

builder.Services.AddControllersWithViews()
    .AddRazorRuntimeCompilation();

3. 封装字符串渲染服务：

public class RazorStringRenderer
{
    private readonly IRazorViewEngine _viewEngine;
    private readonly IServiceProvider _serviceProvider;
    private readonly ITempDataProvider _tempDataProvider;

    public RazorStringRenderer(IRazorViewEngine viewEngine, IServiceProvider serviceProvider, ITempDataProvider tempDataProvider)
    {
        _viewEngine = viewEngine;
        _serviceProvider = serviceProvider;
        _tempDataProvider = tempDataProvider;
    }

    public async Task<string> RenderAsync(string razorContent, object model)
    {
        var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
        var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());

        using var sw = new StringWriter();
        var templateEngine = _viewEngine.Engine;
        var sourceDoc = RazorSourceDocument.Create(razorContent, "temp_template.cshtml");
        var codeDoc = templateEngine.Process(sourceDoc);
        var compiledType = codeDoc.GeneratedCode.Compile();
        var view = (IView)Activator.CreateInstance(compiledType, _viewEngine);

        var viewContext = new ViewContext(
            actionContext,
            view,
            new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary()) { Model = model },
            new TempDataDictionary(httpContext, _tempDataProvider),
            sw,
            new HtmlHelperOptions()
        );

        await view.RenderAsync(viewContext);
        return sw.ToString();
    }
}

4. 注册并使用服务：

// Program.cs注册
builder.Services.AddScoped<RazorStringRenderer>();

// 使用时注入服务
public class YourController : ControllerBase
{
    private readonly RazorStringRenderer _renderer;

    public YourController(RazorStringRenderer renderer)
    {
        _renderer = renderer;
    }

    [HttpPost]
    public async Task<IActionResult> RenderHtml([FromBody] string externalHtml)
    {
        var model = new { /* 你的模型数据 */ };
        string rendered = await _renderer.RenderAsync(externalHtml, model);
        return Ok(rendered);
    }
}

方案三：修复RazorEngine.NET Core版本的空参数错误 #

如果坚持使用原RazorEngine，需确保初始化时参数完整，同时添加系统命名空间：

var config = new TemplateServiceConfiguration
{
    // 必须设置模板管理器，避免空参数错误
    TemplateManager = new ResolvePathTemplateManager(new[] { Directory.GetCurrentDirectory() }),
    // 添加需要的命名空间
    Namespaces = { "System", "System.Math", "System.Convert" }
};

var service = RazorEngineService.Create(config);
string renderedHtml = service.RunCompile(externalHtml, "template_key", null, model);

补充：RazorEngineCore的命名空间配置 #

如果用RazorEngineCore，需手动导入系统命名空间：

var engine = new RazorEngineCore.RazorEngine();
// 全局添加命名空间
engine.DefaultNamespaces.Add("System");

// 编译并渲染
var template = await engine.CompileAsync(externalHtml);
string result = template.Run(model);

内容的提问来源于stack exchange，提问作者Emre Ceylan