原文:
Asp.Net Core 之 @Html.Action 迁移
想必只要 接触了 net core的小伙伴们 已经发现 @html.Action()方法 官方已经不提供支持了，转而使用 ViewComponents替代了，同时也增加了TagHelper。但是 如果想用以前的@Html.Action()方法，我们其实可以自己动手去实现它。
下面就开始 实现之旅吧！
1、创建 静态类 HtmlHelperViewExtensions，其命名空间为 Microsoft.AspNetCore.Mvc.Rendering。这样我们直接用@Html直接可以 使用Action方法了。
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using
Microsoft.AspNetCore.Html;
using
Microsoft.AspNetCore.Http;
using
Microsoft.AspNetCore.Mvc.Infrastructure;
using
Microsoft.AspNetCore.Routing;
using
Microsoft.Extensions.DependencyInjection;
using
System;
using
System.IO;
using
System.Threading.Tasks;
namespace
Microsoft.AspNetCore.Mvc.Rendering
{
public
static
class
HtmlHelperViewExtensions
{
public
static
IHtmlContent Action(
this
IHtmlHelper helper,
string
action,
object
parameters =
null
)
{
var
controller = (
string
)helper.ViewContext.RouteData.Values[
"controller"
];
return
Action(helper, action, controller, parameters);
}
public
static
IHtmlContent Action(
this
IHtmlHelper helper,
string
action,
string
controller,
object
parameters =
null
)
{
var
area = (
string
)helper.ViewContext.RouteData.Values[
"area"
];
return
Action(helper, action, controller, area, parameters);
}
public
static
IHtmlContent Action(
this
IHtmlHelper helper,
string
action,
string
controller,
string
area,
object
parameters =
null
)
{
if
(action ==
null
)
throw
new
ArgumentNullException(
"action"
);
if
(controller ==
null
)
throw
new
ArgumentNullException(
"controller"
);
var
task = RenderActionAsync(helper, action, controller, area, parameters);
return
task.Result;
}
private
static
async Task<IHtmlContent> RenderActionAsync(
this
IHtmlHelper helper,
string
action,
string
controller,
string
area,
object
parameters =
null
)
{
// fetching required services for invocation
var
serviceProvider = helper.ViewContext.HttpContext.RequestServices;
var
actionContextAccessor = helper.ViewContext.HttpContext.RequestServices.GetRequiredService<IActionContextAccessor>();
var
httpContextAccessor = helper.ViewContext.HttpContext.RequestServices.GetRequiredService<IHttpContextAccessor>();
var
actionSelector = serviceProvider.GetRequiredService<IActionSelector>();
// creating new action invocation context
var
routeData =
new
RouteData();
foreach
(
var
router
in
helper.ViewContext.RouteData.Routers)
{
routeData.PushState(router,
null
,
null
);
}
routeData.PushState(
null
,
new
RouteValueDictionary(
new
{ controller = controller, action = action, area = area }),
null
);
routeData.PushState(
null
,
new
RouteValueDictionary(parameters ??
new
{ }),
null
);
//get the actiondescriptor
RouteContext routeContext =
new
RouteContext(helper.ViewContext.HttpContext) { RouteData = routeData };
var
candidates = actionSelector.SelectCandidates(routeContext);
var
actionDescriptor = actionSelector.SelectBestCandidate(routeContext, candidates);
var
originalActionContext = actionContextAccessor.ActionContext;
var
originalhttpContext = httpContextAccessor.HttpContext;
try
{
var
newHttpContext = serviceProvider.GetRequiredService<IHttpContextFactory>().Create(helper.ViewContext.HttpContext.Features);
if
(newHttpContext.Items.ContainsKey(
typeof
(IUrlHelper)))
{
newHttpContext.Items.Remove(
typeof
(IUrlHelper));
}
newHttpContext.Response.Body =
new
MemoryStream();
var
actionContext =
new
ActionContext(newHttpContext, routeData, actionDescriptor);
actionContextAccessor.ActionContext = actionContext;
var
invoker = serviceProvider.GetRequiredService<IActionInvokerFactory>().CreateInvoker(actionContext);
await invoker.InvokeAsync();
newHttpContext.Response.Body.Position = 0;
using
(
var
reader =
new
StreamReader(newHttpContext.Response.Body))
{
return
new
HtmlString(reader.ReadToEnd());
}
}
catch
(Exception ex)
{
return
new
HtmlString(ex.Message);
}
finally
{
actionContextAccessor.ActionContext = originalActionContext;
httpContextAccessor.HttpContext = originalhttpContext;
if
(helper.ViewContext.HttpContext.Items.ContainsKey(
typeof
(IUrlHelper)))
{
helper.ViewContext.HttpContext.Items.Remove(
typeof
(IUrlHelper));
}
}
}
}
}
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2、 在Startup中的 ConfigureServices 方法添加：
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor();
services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
（备注：因为net core 默认不将IHttpContextAccessor，IActionContextAccessor 依赖注入，所以需要手动进行依赖注入）
3、在页面中，我们就可以直接用 @Html.Action()方法 直接请求 控制器的方法了。
4、小结：如今微软官方已经提供了 新的 TagHelper、View components 来替代之前的写法。这个教程只适用于对视图层不想做更变的小伙伴使用。如果 是新项目的，还是建议使用 View components!
转自:https://blog.csdn.net/huanghuangtongxue/article/details/78987833
来源：oschina
链接：https://my.oschina.net/u/4284954/blog/4289043