I've got an asp.net core 2.2 project with a startup.cs service that does an async REST GET call back to my current site and then returns the result (View Component using DI) back to the razor view.
In the service, I want to call "/api/sessions" and not "http://localhost:3433/api/sessions". I know I could use the ~ ta helper if I were inside my razor page to get the base path to the web server, but how can I get that from a service?
Here is my service and relevant code.
From: SessionsService.cs (this is where I don't want http://localhost but just ~/
public class Session
{
public int Id { get; set; }
public string Title { get; set; }
public string Description { get; set; }
}
public class SessionsService : ISessionsService
{
public async Task<List<Session>> GetSessions(int speakerId)
{
var uri = new Uri("http://localhost:50463/api/sessions");
var httpClient = new HttpClient();
var result = await httpClient.GetStringAsync(uri);
var sessions = JsonConvert.DeserializeObject<List<Session>>(result);
return sessions;
}
}
From: startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddTransient<ISessionsService, SessionsService>();
From: index.cshtml
<vc:speaker-card speaker="#speaker" ></vc:speaker-card>
From: SpeakerCardViewComponent.cs
{
private ISessionsService _sessionsService;
public SpeakerCardViewComponent(ISessionsService sessionsService)
{
_sessionsService = sessionsService;
}
public async Task<IViewComponentResult> InvokeAsync(
Speaker speaker)
{
var sessions = await _sessionsService.GetSessions(101);
speaker.Sessions = sessions;
return View(speaker);
}
}
ANSWER AS SUGGESTED BY KIRK LARKIN FOLLOWS:
public async Task<List<Session>> GetSessions(int speakerId,string baseUrl)
{
var uri = new Uri($"{baseUrl}api/sessions");
var httpClient = new HttpClient();
var result = await httpClient.GetStringAsync(uri);
var sessions = JsonConvert.DeserializeObject<List<Session>>(result);
return sessions;
}
public void ConfigureServices(IServiceCollection services)
{
services.AddTransient<ISessionsService, SessionsService>();
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
public class SpeakerCardViewComponent : ViewComponent
{
private ISessionsService _sessionsService;
private IHttpContextAccessor _httpContextAccessor;
public SpeakerCardViewComponent(ISessionsService sessionsService, IHttpContextAccessor httpContextAccessor)
{
_sessionsService = sessionsService;
_httpContextAccessor = httpContextAccessor;
}
public async Task<IViewComponentResult> InvokeAsync(
Speaker speaker)
{
var isHttps = _httpContextAccessor.HttpContext.Request.IsHttps;
var baseUrl = isHttps ? "https://" : "http://"
+ _httpContextAccessor.HttpContext.Request.Host.Value
+ "/";
var sessions = await _sessionsService.GetSessions(speaker.SpeakerId, baseUrl);
speaker.Sessions = sessions;
return View(speaker);
}
}
I want to take a few post query parameters from an API i have and create a new entry. I wanted to do this with in the method with out needing to load context or something.
namespace fais.printing_services.Controllers
{
[Produces("application/json")]
[Route("api/[controller]/[action]")]
public class printController : Controller
{
private readonly IHostingEnvironment _appEnvironment;
public printController(IHostingEnvironment appEnvironment)
{
_appEnvironment = appEnvironment;
}
/**/
[HttpPost]
public IActionResult request(string id="test_default", string url = "", string html = "")
{
print_job _print_job = new print_job();
_print_job.html = html;
_print_job.options = options; //json object string
_print_job.url = url;
using (ApplicationDbContext db = new ApplicationDbContext())
{
db.print_job.Add(_print_job);
db.SaveChanges();
}
return Json(new
{
save = true
});
}
}
}
I just want to be able create a new print_job entry and save it when the API is called and return a json response.
Add ApplicationDbContext to controller constructor, it will be injected automatically (if your Startup.cs is like recommeneded):
private readonly IHostingEnvironment _appEnvironment;
private readonly ApplicationDbContext _db;
public printController(IHostingEnvironment appEnvironment, ApplicationDbContext db)
{
_appEnvironment = appEnvironment;
_db = db;
}
[HttpPost]
public IActionResult request(string id="test_default", string url = "", string html = "")
{
var _print_job = new print_job()
{
html = html,
options = options,
url = url,
}
_db.print_job.Add(_print_job);
_db.SaveChanges();
return Json(new { save = true });
}
I'm trying to upload a file using ASP.NET Core Web Api.
As many i found this code:
namespace ModelBindingWebSite.Controllers
{
public class HomeController : Controller
{
private IHostingEnvironment _environment;
public HomeController(IHostingEnvironment environment)
{
_environment = environment;
}
public IActionResult Index()
{
return View();
}
[HttpPost]
public async Task<IActionResult> Index(ICollection<IFormFile> files)
{
var uploads = Path.Combine(_environment.WebRootPath, "uploads");
foreach (var file in files)
{
if (file.Length > 0)
{
var fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');
await file.SaveAsAsync(Path.Combine(uploads, fileName));
}
}
return View();
}
}
I get the error IFormFile does not contain a definition for SaveAsASync and no extension method.
Any idea?
You can simply build a handy extension for later use
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
public static class FileSaveExtension
{
public static async Task SaveAsAsync(this IFormFile formFile, string filePath)
{
using (var stream = new FileStream(filePath, FileMode.Create))
{
await formFile.CopyToAsync(stream);
}
}
public static void SaveAs(this IFormFile formFile, string filePath)
{
using (var stream = new FileStream(filePath, FileMode.Create))
{
formFile.CopyTo(stream);
}
}
}
Implementation:
formFile.SaveAsAsync("Your-File-Path"); // [ Async call ]
formFile.SaveAs("Your-File-Path");
Please see https://github.com/aspnet/HttpAbstractions/issues/610 which explains why the method has been superceded
Is it possible to invoke a View Component from controller and render it to a string? I am really looking for some code example for this. Any help will be much appreciated.
As of beta7 it is now possible to return a ViewComponent directly from a controller. Check the MVC/Razor section of the announcement
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.
So now the code for returning the sample view component just needs to be:
public class HomeController : Controller
{
public IActionResult Index()
{
return ViewComponent("My");
}
}
Please refer to example from official ASP.NET article on ViewComponent
In their example, the view component is called directly from the controller as follows:
public IActionResult IndexVC()
{
return ViewComponent("PriorityList", new { maxPriority = 3, isDone = false });
}
You can do that but you have to apply following thing as It is render by DefaultViewComponentHelper.
You have to create instance of this and to create that you need IViewComponentSelector and IViewComponentInvokerFactory.
To do this I have done following thing.
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();
}
}
Here is my sample View Component.
public class MyViewComponent : ViewComponent
{
public MyViewComponent()
{
}
public IViewComponentResult Invoke()
{
return Content("This is test");
}
}
Here's a tag helper that I created to embed components via HTML like syntax. Invoking from a TagHelper like this should closely match invoking from a Controller.
ViewComponent Tag Helper
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)
);
}
}
}
Usage
<component name="RecentComments" params="new { take: 5, random: true }"></component>
Code from dotnetstep's answer updated for MVC 6.0.0-beta4 (VS2015 RC):
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();
}
}
Based on https://gist.github.com/pauldotknopf/b424e9b8b03d31d67f3cce59f09ab17f
public class HomeController : Controller
{
public async Task<string> RenderViewComponent(string viewComponent, object args)
{
var sp = HttpContext.RequestServices;
var helper = new DefaultViewComponentHelper(
sp.GetRequiredService<IViewComponentDescriptorCollectionProvider>(),
HtmlEncoder.Default,
sp.GetRequiredService<IViewComponentSelector>(),
sp.GetRequiredService<IViewComponentInvokerFactory>(),
sp.GetRequiredService<IViewBufferScope>());
using (var writer = new StringWriter())
{
var context = new ViewContext(ControllerContext, NullView.Instance, ViewData, TempData, writer, new HtmlHelperOptions());
helper.Contextualize(context);
var result = await helper.InvokeAsync(viewComponent, args);
result.WriteTo(writer, HtmlEncoder.Default);
await writer.FlushAsync();
return writer.ToString();
}
}
}
and
public class NullView : IView
{
public static readonly NullView Instance = new();
public string Path => string.Empty;
public Task RenderAsync(ViewContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
return Task.CompletedTask;
}
}
im building a site using MVC4 and i want to display a navigation bar at the top of my _ViewStart according to my Database.
How can i do so? can i use a contoroller ActionResult that fired once the index page is loaded?
or how can i triger it by a partial view
my current ActionResult returning partial view is:
public ActionResult NavigationBar()
{
var entities = new CakesDBEntities();
var articles = entities.Articles;
List<NavBarModel> navBarList = articles.Select(nb => new NavBarModel { Title = nb.title, Url = nb.url }).ToList();
return View(navBarList);
}
my model:
namespace SimplyCakes20131009.Models
{
public class NavBarModel
{
public string Title { get; set; }
public string Url { get; set; }
}
}
my partial view:
#model IEnumerable<SimplyCakes20131009.Models.NavBarModel>
#foreach (var bar in Model)
{
<li>
#Html.ActionLink(bar.Title, bar.Url)
</li>
}
How can i integrate the nav bar to my _ViewStart?
A better option would be to use the _Layout.cshtml. _ViewStart is just calls the _Layout.cshtml.
You probably don't need partial View here. You can use a Child Action that renders PartialView results.
In your
_Layout.cshtml :
You can have
#{ Html.RenderAction("Navigation", "Home"); }
This points to the HomeController and Navigation Action
Additional Note: Html.RenderAction better because it is much faster than the Html.Action.
It can handle large amount of HTML efficiently as it will directly send the result to the Response. Html.Action just returns a strings with the result.
Navigation Action has its Navigation View which is pretty much equivalent to what you had in your view.
Home/Navigation.cshtml :
#model IEnumerable<MvcApplication1.Controllers.NavViewModel>
#foreach (var nav in Model)
{
<li>#Html.ActionLink(nav.Title, nav.Url)</li>
}
HomeController.cs :
Note that you probably inject the DB access as dependency to support the testability.
public class HomeController : Controller
{
private readonly ICakesRepository _cakesRepository;
//additional constructor to support testability.
public HomeController(ICakesRepository cakesRepository) {
_cakesRepository = cakesRepository;
}
//this can be removed if you the above with IOC/DI wire-up
public HomeController() {
_cakesRepository = new CakesRepository();
}
[ChildActionOnly]
[HttpGet]
public ActionResult Navigation() {
var articles = _cakesRepository.GetArticles();
var navBarList = articles.Select(nb => new NavViewModel { Title = nb.Title, Url = nb.Url });
return PartialView(navBarList);
}
}
Additional supporting classes :
public class NavViewModel {
public string Title { get; set; }
public string Url { get; set; }
}
public interface ICakesRepository {
IEnumerable<Articles> GetArticles();
}
public class CakesRepository : ICakesRepository {
public IEnumerable<Articles> GetArticles() {
//call to a db
//fake db data
return new List<Articles>() {
new Articles(){Title = "Title1", Url = "http://urlone.com"},
new Articles(){Title = "Title2", Url = "http://urltwo.com"},
new Articles(){Title = "Title3", Url = "http://urlthree.com"}
};
}
}
public class Articles {
public string Title { get; set; }
public string Url { get; set; }
}