如何使用razor只返回html正文的内容？

在使用ASP.NET Core的Razor视图引擎时，如果你想要从视图中提取并返回纯HTML内容，可以通过以下几种方法实现：

方法一：使用`View()`方法

在你的控制器中，你可以直接调用View()方法来渲染视图，并获取渲染后的HTML内容。

public IActionResult GetHtmlContent()
{
    var result = View("YourViewName").Result;
    var htmlContent = ((ViewResult)result).View.Render(result.ViewData, result.TempDataProvider, result.Writer);
    return Content(htmlContent.ToString(), "text/html");
}

方法二：使用`RazorViewEngine`

你可以使用RazorViewEngine来编译和渲染视图，从而获取HTML内容。

public IActionResult GetHtmlContent()
{
    var viewEngine = new RazorViewEngine();
    var viewPath = "~/Views/YourControllerName/YourViewName.cshtml";
    var view = viewEngine.FindView(ControllerContext, viewPath, false);

    if (view.View == null)
    {
        throw new ArgumentNullException($"{viewPath} does not match any available view");
    }

    var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary());
    var viewContext = new ViewContext(ControllerContext, view.View, viewDictionary, new TempDataDictionary(), TextWriter.Null, new HtmlHelperOptions());

    using (var output = new StringWriter())
    {
        view.View.Render(viewContext, output);
        var htmlContent = output.ToString();
        return Content(htmlContent, "text/html");
    }
}

方法三：使用`IViewRenderService`

你可以创建一个服务来处理视图的渲染，这样可以更好地解耦和控制。

首先，定义一个接口：

public interface IViewRenderService
{
    Task<string> RenderToStringAsync(string viewName, object model);
}

然后，实现这个接口：

public class ViewRenderService : IViewRenderService
{
    private readonly IRazorViewEngine _razorViewEngine;
    private readonly ITempDataProvider _tempDataProvider;
    private readonly IServiceProvider _serviceProvider;

    public ViewRenderService(IRazorViewEngine razorViewEngine, ITempDataProvider tempDataProvider, IServiceProvider serviceProvider)
    {
        _razorViewEngine = razorViewEngine;
        _tempDataProvider = tempDataProvider;
        _serviceProvider = serviceProvider;
    }

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

        using (var sw = new StringWriter())
        {
            var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);

            if (viewResult.View == null)
            {
                throw new ArgumentNullException($"{viewName} does not match any available view");
            }

            var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
            {
                Model = model
            };

            var viewContext = new ViewContext(
                actionContext,
                viewResult.View,
                viewDictionary,
                new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
                sw,
                new HtmlHelperOptions()
            );

            await viewResult.View.RenderAsync(viewContext);
            return sw.ToString();
        }
    }
}

在Startup.cs中注册这个服务：

public void ConfigureServices(IServiceCollection services)
{
    services.AddRazorPages();
    services.AddScoped<IViewRenderService, ViewRenderService>();
}

最后，在控制器中使用这个服务：

public class YourController : Controller
{
    private readonly IViewRenderService _viewRenderService;

    public YourController(IViewRenderService viewRenderService)
    {
        _viewRenderService = viewRenderService;
    }

    public async Task<IActionResult> GetHtmlContent()
    {
        var htmlContent = await _viewRenderService.RenderToStringAsync("YourViewName", new YourModel());
        return Content(htmlContent, "text/html");
    }
}