如何从控制器调用视图组件

Question

是否可以从控制器调用视图组件并将其呈现为字符串？我真的在为此寻找一些代码示例。任何帮助将不胜感激。

Answer 1

您可以这样做，但您必须应用以下内容，因为它是由 DefaultViewComponentHelper 呈现的。

您必须创建此实例并创建您需要的 IViewComponentSelector 和 IViewComponentInvokerFactory。

为此我做了以下事情。

public class HomeController : Controller
    {
        Microsoft.AspNet.Mvc.DefaultViewComponentHelper helper = null;
        Microsoft.AspNet.Mvc.Razor.RazorView razorView = null;
        public HomeController(IViewComponentSelector selector,IViewComponentInvokerFactory factory,IRazorPageFactory razorPageFactory,IRazorPageActivator pageActivator,IViewStartProvider viewStartProvider)
        {
            helper = new DefaultViewComponentHelper(selector, factory);
            razorView = new Microsoft.AspNet.Mvc.Razor.RazorView(razorPageFactory, pageActivator, viewStartProvider);           
        }
        public IActionResult Index()
        {                  
            ViewContext context = new ViewContext(ActionContext, razorView, ViewData, null);
            helper.Contextualize(context);
            string st1 = helper.Invoke("My", null).ToString();
            return View();
        }
}

这是我的示例视图组件。

 public class MyViewComponent : ViewComponent
    {     

        public MyViewComponent()
        {

        }

        public IViewComponentResult Invoke()
        {
            return Content("This is test");
        }
    }

Answer 2

dotnetstep 的答案中的代码针对 MVC 6.0.0-beta4 (VS2015 RC) 进行了更新：

public class HomeController : Controller
    {
        Microsoft.AspNet.Mvc.ViewComponents.DefaultViewComponentHelper helper = null;

        public HomeController(IViewComponentDescriptorCollectionProvider descriptorProvider, IViewComponentSelector selector, IViewComponentInvokerFactory invokerFactory)
        {
            helper = new DefaultViewComponentHelper(descriptorProvider, selector, invokerFactory);
        }
        public IActionResult Index()
        {                  
            ViewContext context = new ViewContext(ActionContext, null, ViewData, null, null);
            helper.Contextualize(context);
            string st1 = helper.Invoke("My", null).ToString();
            return View();
        }
}

Answer 3

从 beta7 开始，现在可以 return 直接从控制器访问 ViewComponent。检查 the announcement

的 MVC/Razor 部分

The new ViewComponentResult in MVC makes it easy to return the result of a ViewComponent from an action. This allows you to easily expose the logic of a ViewComponent as a standalone endpoint.

所以现在 return 示例视图组件的代码只需要是：

public class HomeController : Controller
{
    public IActionResult Index()
    {
        return ViewComponent("My");
    }
}

Answer 4

这是我创建的一个标签助手，用于通过类似 HTML 的语法嵌入组件。像这样从 TagHelper 调用应该与从 Controller 调用非常匹配。

ViewComponent 标签助手

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewComponents;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;


namespace TagHelperSamples.Web
{
    [HtmlTargetElement("component")]
    public class ComponentTagHelper : TagHelper
    {
        private DefaultViewComponentHelper _componentHelper;

        [HtmlAttributeName("name")]
        public string Name { get; set; }

        [HtmlAttributeName("params")]
        public object Params { get; set; }

        [ViewContextAttribute] // inform razor to inject
        public ViewContext ViewContext { get; set; }

        public ComponentTagHelper(IViewComponentHelper componentHelper)
        {
            _componentHelper = componentHelper as DefaultViewComponentHelper;
        }

        public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
        {       
            _componentHelper.Contextualize(ViewContext);

            output.Content.AppendHtml(
                await _componentHelper.InvokeAsync(Name, Params)
            );
        }
    }
}

用法

<component name="RecentComments" params="new { take: 5, random: true }"></component>

Answer 5

请参考official ASP.NET article on ViewComponent

中的例子

在他们的示例中，视图组件是直接从控制器调用的，如下所示：

public IActionResult IndexVC()
{
    return ViewComponent("PriorityList", new { maxPriority = 3, isDone = false });
}

如何从控制器调用视图组件

How to invoke a View Component from controller

asp.net-core

asp.net-core-mvc