使用 ASP.NET Core 将 Razor 视图预编译为字符串答案

【问题标题】：Pre-compiled Razor view to string with ASP.NET Core使用 ASP.NET Core 将 Razor 视图预编译为字符串
【发布时间】：2016-12-04 23:21:41
【问题描述】：

如何在使用 ASP.NET Core 1.1 的新 Razor 预编译时将 Razor 视图呈现为字符串？

以下代码来自示例，由于viewResult.View 为空，将引发异常。

var httpContext = new DefaultHttpContext { RequestServices = _serviceProvider };
var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());

var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);

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

https://blogs.msdn.microsoft.com/webdev/2016/10/25/announcing-asp-net-core-1-1-preview-1/

旧方式（示例）：File -> Razor -> Compile -> string

【问题讨论】：

标签： c# asp.net-mvc razor asp.net-core

【解决方案1】：

它应该已经工作了。当你打电话时：

viewResult.View.RenderAsync(viewContext);

它将找到预编译的视图并使用该视图，而不是再次编译该视图。

【讨论】：

在到达这行代码之前抛出异常。
我有同样的问题，这不是解决方案。作为@SeriousK。表示错误是在该行之前引发的。
看看stackoverflow.com/a/50680245/1358684，如果有帮助就接受它作为答案。

【解决方案2】：

您必须实现 IViewRenderService 并在您的 Startup.cs 中注册。然后添加这样的函数：

public class ViewRenderService : IViewRenderService
{
    private readonly ITempDataProvider _tempDataProvider;
    private readonly IServiceProvider _serviceProvider;
    private readonly HttpContext _context;
    private readonly ICompositeViewEngine _viewEngine;
    private const string ControllerStr = "controller";

    public ViewRenderService(
        ITempDataProvider tempDataProvider,
        IServiceProvider serviceProvider,
        IHttpContextAccessor accessor,
        ICompositeViewEngine viewEngine)
    {
        _tempDataProvider = tempDataProvider;
        _serviceProvider = serviceProvider;
        _context = accessor.HttpContext;
        _viewEngine = viewEngine;
    }

    public async Task<string> RenderToStringAsync(string viewName, object model)
    {
        return await RenderToStringAsync(viewName, model, null);
    }

    public async Task<string> RenderToStringAsync(string viewName, object model, ViewDataDictionary viewDataDictionary)
    {
        var controller = string.Empty;
        viewName = viewName?.TrimStart(new char[] { '/' });
        Regex rex = new Regex(@"^(\w+)\/(.*)$");
        Match match = rex.Match(viewName);
        if (match.Success)
        {
            controller = match.Groups[1].Value;
            viewName = match.Groups[2].Value;
        }

        var routeData = new RouteData();
        routeData.Values.Add(ControllerStr, controller);
        var actionContext = new ActionContext(_context, routeData, new ActionDescriptor());

        var viewResult = _viewEngine.FindView(actionContext, viewName, false);

        if (viewResult.View == null)
        {
            Console.WriteLine($"Searched the following locations: {string.Join(", ", viewResult.SearchedLocations)} for folder \"{controller}\" and view \"{viewName}\"");
            throw new ArgumentNullException($"{viewName} does not match any available view");
        }

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

        if (viewDataDictionary != null)
        {
            foreach (var obj in viewDataDictionary)
            {
                viewDictionary.Add(obj);
            }
        }

        using (var sw = new StringWriter())
        {
            var viewContext = new ViewContext(
                actionContext,
                viewResult.View,
                viewDictionary,
                new TempDataDictionary(_context, _tempDataProvider),
                sw,
                new HtmlHelperOptions()
            );
            viewContext.RouteData = _context.GetRouteData();

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

【讨论】：