How does Asp.net Core renders a view - razor

Question

How does MVC 6 renders a view. What's the actual method in Razor ViewEngine that generates the html output? Also if possible please explain the process of rendering a view.
May be you could point me to a file on mvc source on github. thanks!

Answer 1

Here is a complete solution of what you are looking for. I used dependency injection to get the HtmlHelper in the controller. You can inject your own helper if you want too.
using Microsoft.AspNet.Html.Abstractions;
using Microsoft.AspNet.Mvc;
using Microsoft.AspNet.Mvc.ModelBinding;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewEngines;
using Microsoft.AspNet.Mvc.ViewFeatures;
using Microsoft.AspNet.Mvc.ViewFeatures.Internal;
using Microsoft.Extensions.WebEncoders;
using System.ComponentModel.DataAnnotations;
using System;
public class MyController : Controller
{
private readonly IHtmlGenerator htmlGenerator;
ICompositeViewEngine viewEngine;
IModelMetadataProvider metadataProvider;
private readonly IHtmlHelper helper;
IHtmlEncoder htmlEncoder;
IUrlEncoder urlEncoder;
IJavaScriptStringEncoder javaScriptStringEncoder;
public MyController(IHtmlHelper helper, IHtmlGenerator htmlGenerator, ICompositeViewEngine viewEngine, IModelMetadataProvider metadataProvider, IHtmlEncoder htmlEncoder, IUrlEncoder urlEncoder, IJavaScriptStringEncoder javaScriptStringEncoder)
{
this.htmlGenerator = htmlGenerator;
this.viewEngine = viewEngine;
this.metadataProvider = metadataProvider;
this.htmlEncoder = htmlEncoder;
this.urlEncoder = urlEncoder;
this.javaScriptStringEncoder = javaScriptStringEncoder;
this.helper = helper;
}
[HttpGet]
public IActionResult MyHtmlGenerator()
{
MyViewModel temp = new MyViewModel();
var options = new HtmlHelperOptions();
options.ClientValidationEnabled = true;
ViewDataDictionary<MyViewModel> dic = new ViewDataDictionary<MyViewModel>(this.metadataProvider, new ModelStateDictionary());
ViewContext cc = new ViewContext(ActionContext, new FakeView(), dic, TempData, TextWriter.Null, options);
var type = typeof(MyViewModel);
var metadata = this.metadataProvider.GetMetadataForType(type);
ModelExplorer modelEx = new ModelExplorer(this.metadataProvider, metadata, temp);
ViewData["Description"] = "test desc";
ViewData["Id"] = 1;
this.ViewData = new ViewDataDictionary(this.metadataProvider, new ModelStateDictionary());
IHtmlHelper<MyViewModel> dd = new HtmlHelper<MyViewModel>(this.htmlGenerator, this.viewEngine, this.metadataProvider, this.htmlEncoder, this.urlEncoder, this.javaScriptStringEncoder);
((ICanHasViewContext)dd).Contextualize(cc);
dd.ViewContext.ViewData = this.ViewData;
var desc = GetString(dd.TextBoxFor(m => m.ID));
var ID = GetString(dd.TextBoxFor(m => m.Description));
// Do whatever you want with the ID and desc
return new ContentResult() { Content = ID + desc };
}
public static string GetString(IHtmlContent content)
{
var writer = new System.IO.StringWriter();
content.WriteTo(writer, new HtmlEncoder());
return writer.ToString();
}
}
public class MyViewModel : BaseAssetViewModel
{
// [RegularExpression(#"^-?\d{1,13}(\.\d{0,5})?$|^-?\.\d{1,5}$")]
[Required]
public int ID { get; set; }
[MinLength(2)]
public string Description { get; set; }
// Property with no validation
public string Other { get; set; }
}
public class FakeView : IView
{
string IView.Path
{
get
{
throw new NotImplementedException();
}
}
public Task RenderAsync(ViewContext viewContext)
{
throw new InvalidOperationException();
}
Task IView.RenderAsync(ViewContext context)
{
throw new NotImplementedException();
}
}

Answer 2

I don't know if this may be of help, may be you have to start to look at tag helpers:
https://github.com/DamianEdwards/TagHelperStarterWeb
they're working to a different way to create helpers that integrate in the page in a more natural way.