I am migrating some old code where HtmlTextWriter is used extensively to render UI elements.
I am migrating the code to use ASP.NET MVC 1.0. As far as I am aware, I am not using any of the HtmlTextWriter specific function (such as indentation).
Currently, I am using a wrapper method to return string generated by the HtmlTextWriter as follow:
var sw = new StringWriter();
var xhtmlTextWriter = new XhtmlTextWriter(sw);
GenerateHtml(xhtmlTextWriter);
return sw.ToString();
My questions are:
I am trying to get HtmlTextWriter instance from ASP.NET MVC View, but apparently even the HtmlHelper does not use this. Do I miss anything?
Each call to GenerateHtml will generated small HTML pieces, generally not bigger than 1000 characters, but there can be a lot of calls. Is it worth rewriting the HtmlTextWriter dependent code into StringBuilder? Or instead, what about creating a HtmlTextWriter instance which will be used on all calls (and flushed at the end of the iterations).
Instead of creating a StringBuider and StringWriter I think using the helper.ViewContext.writer will work.
Then the above sample code would be:
var calendar = new DayPilotCalendar();
if( model != null )
{
model.CopyTo( calendar );
}
if( options != null )
{
options.CopyTo( calendar );
}
HtmlTextWriter writer = new HtmlTextWriter( helper.ViewContext.Writer );
writer.AddAttribute( HtmlTextWriterAttribute.Class, "dayPilot" );
writer.RenderBeginTag( HtmlTextWriterTag.Div );
calendar.RenderControl( writer );
writer.RenderEndTag(); // Close DIV
return( null ); // Don't need to return anything.
Disclaimer: So far I've only tried using the helper.ViewContext.Writer to produce a <UL> list. It worked fine. Haven't tried it to render controls.
I have a demo app here which shows how to do this in an MVC app.
Here's a code sample, from that post.
public static string DayPilot(
this HtmlHelper helper,
DayPilotData model,
DayPilotViewOptions options)
{
var calendar = new DayPilotCalendar();
if (model != null)
{
model.CopyTo(calendar);
}
if (options != null)
{
options.CopyTo(calendar);
}
var sb = new System.Text.StringBuilder();
sb.Append("<div class=\"dayPilot\">"); // allows working around td cellpadding bug in css
using (var sw = new System.IO.StringWriter(sb))
{
using (var tw = new HtmlTextWriter(sw))
{
calendar.RenderControl(tw);
}
}
sb.Append("</div>");
return sb.ToString();
}
Regarding #2, if it ain't broke...
Related
I'm trying to build a very simple website to display some test data being added & updated using asp.net mvc (with razor) but whenever data is posted to my Post method, my data is not being updated. I'm trying to get a unordered list (for now) to be updated the second a post is triggered.
I'm posting my data as JSON using the following code:
string jsonDeviceData = SerializeHelper.Serialize<IDeviceData>(deviceData,
ContentTypeEnum.Json, false);
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(localServerUrl);
webRequest.Method = "POST";
webRequest.ContentType = "application/json"; //"application/x-www-form-urlencoded";
byte[] deviceDataBuffer = Encoding.UTF8.GetBytes(jsonDeviceData);
Task<Stream> requestTask = webRequest.GetRequestStreamAsync();
using (Stream requestStream = requestTask.Result)
{
requestStream.Write(deviceDataBuffer, 0, deviceDataBuffer.Length);
}
Task<WebResponse> responseTask = webRequest.GetResponseAsync();
using (StreamReader requestReader = new StreamReader(responseTask.Result
.GetResponseStream()))
{
string webResponse = requestReader.ReadToEnd();
Debug.WriteLine("Web Response: " + webResponse);
}
Below is the code I'm using in the POST method. Don't worry about the logic being so simplistic and probably horrible, but I'm just dabbling with this idea. Data will be stored in SQL Server database and I'll use EF if I decide to go further with this:
[HttpPost()]
public ActionResult Index(DeviceModel model)
{
if (ModelState.IsValid && model != null)
{
var deviceViewModelList = HttpContext.Application["DeviceList"]
as List<DeviceViewModel> ?? new List<DeviceViewModel>();
if (deviceViewModelList.All(m => !string.Equals(m.Name,
model.Name,
StringComparison.InvariantCultureIgnoreCase)))
{
deviceViewModelList.Add(new DeviceViewModel(model));
}
HttpContext.Application["DeviceList"] = deviceViewModelList;
var homePageViewModel = new HomePageViewModel
{
DeviceList = deviceViewModelList
};
return RedirectToAction("Index");
}
else
{
return View();
}
}
My model is passed correctly and everything works ok when the data is posted my page is not updated, even after calling RedirectToAction("Index");
The code below gets called the first time the page is loaded and after calling the RedirectToActio("Index"):
public ActionResult Index()
{
ViewBag.Title = "Test Server";
var deviceViewModelList = HttpContext.Application["DeviceList"]
as List<DeviceViewModel> ?? new List<DeviceViewModel>();
var homePageViewModel = new HomePageViewModel
{
DeviceList = deviceViewModelList
};
return View(homePageViewModel);
}
This is the code I have in my .cshtml page:
<ul>
#if (Model?.DeviceList != null)
{
foreach (var device in Model.DeviceList)
{
<li>#device.Name</li>
}
}
</ul>
If I check Fiddler, the data, in this case, the list is build correctly.
If I press F5 my data is displayed correctly.
I've read so many articles at this stage and I still haven't got a solution, one of them being View not updated after post and while I've tried ModelState.Clear(); and as you can see from my code I'm using #device.Name which is one of the suggestion. I'm not sure about the last one.
Another article I read was ASP NET MVC Post Redirect Get Pattern but again to no avail.
I'm obviously missing something.
Most articles/samples I've been looking at refer to posting via a Form and I know I'm posting, but is that the same as posting via a Form?
Also my page's viewModel is for my page and it contains a list of devices. Is that OK rather than passing the list of device as the viewmodel to the page? The reason I'm doing this is that I will want to access other lists at a later stage.
Has anyone got any suggestions?
Much appreciated.
I am just new in MVC 4. I have a html Razor view which contain all some table related data.
I just want to convert that view in to pdf document without third-party tool.
In case you are using ASP.NET Core here is my solution: http://nikolay.it/Blog/2018/03/Generate-PDF-file-from-Razor-view-using-ASP-NET-Core-and-PhantomJS/37
Get HTML string from a Razor view
This step is pretty straight-forward. There is a service called IRazorViewEngine in ASP.NET Core which can be injected and then used to get the view. After providing the view with default ViewDataDictionary and ActionContext we can request the view to be rendered into StringWriter which can be easily converted to string. Here is ready-to-use code for getting a string from given Razor view file:
public interface IViewRenderService
{
Task<string> RenderToStringAsync(string viewName, object model);
}
public class ViewRenderService : IViewRenderService
{
private readonly IRazorViewEngine razorViewEngine;
private readonly ITempDataProvider tempDataProvider;
private readonly IServiceProvider serviceProvider;
public ViewRenderService(
IRazorViewEngine razorViewEngine,
ITempDataProvider tempDataProvider,
IServiceProvider serviceProvider)
{
this.razorViewEngine = razorViewEngine;
this.tempDataProvider = tempDataProvider;
this.serviceProvider = serviceProvider;
}
public async Task<string> RenderToStringAsync(string viewName, object model)
{
var httpContext = new DefaultHttpContext { RequestServices = this.serviceProvider };
var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
using (var sw = new StringWriter())
{
var viewResult = this.razorViewEngine.GetView(null, viewName, false);
if (viewResult.View == null)
{
throw new ArgumentNullException($"{viewName} does not match any available view");
}
var viewDictionary =
new ViewDataDictionary(
new EmptyModelMetadataProvider(),
new ModelStateDictionary()) { Model = model };
var viewContext = new ViewContext(
actionContext,
viewResult.View,
viewDictionary,
new TempDataDictionary(actionContext.HttpContext, this.tempDataProvider),
sw,
new HtmlHelperOptions());
await viewResult.View.RenderAsync(viewContext);
return sw.ToString();
}
}
}
One important think here: if you use view compilation (pre-compiling views to YourProject.Web.PrecompiledViews.dll) then it is important to get the view using the GetView method instead of FindView. More information here.
Generate the PDF file from HTML using PhantomJS
For this task we are going to use a headless browser which will render the HTML (with all CSS and JS included in it). There are many such tools but I will use PhantomJS (headless WebKit scriptable with a JavaScript API). PhantomJS can save the rendered page to small-sized PDF pretty fast. For the PDF export to work we are going to need a .js file which will use the PhantomJS API to tell the tool that we want to export the file:
"use strict";
var page = require('webpage').create(),
system = require('system'),
address,
output;
console.log('Usage: rasterize.js [URL] [filename] [paperformat]');
address = system.args[1];
output = system.args[2];
page.viewportSize = { width: 600, height: 600 };
page.paperSize = { format: system.args[3], orientation: 'portrait', margin: '0.5cm' };
page.open(address, function (status) {
if (status !== 'success') {
console.log('Unable to load the address!');
phantom.exit(1);
} else {
window.setTimeout(function () {
page.render(output);
phantom.exit();
}, 200);
}
});
The next thing is to run the phantomjs.exe process and pass the rasterize.js file along with paths for the HTML file and the output file name for the PDF result. This is done in HtmlToPdfConverter.cs:
public interface IHtmlToPdfConverter
{
byte[] Convert(string htmlCode);
}
public class HtmlToPdfConverter : IHtmlToPdfConverter
{
public byte[] Convert(string htmlCode)
{
var inputFileName = "input.html";
var outputFileName = "output.pdf";
File.WriteAllText(inputFileName, htmlCode);
var startInfo = new ProcessStartInfo("phantomjs.exe")
{
WorkingDirectory = Environment.CurrentDirectory,
Arguments = string.Format(
"rasterize.js \"{0}\" {1} \"A4\"",
inputFileName,
outputFileName),
UseShellExecute = true,
};
var process = new Process { StartInfo = startInfo };
process.Start();
process.WaitForExit();
var bytes = File.ReadAllBytes(outputFileName);
File.Delete(inputFileName);
File.Delete(outputFileName);
return bytes;
}
}
If you are going to deploy your application in Azure it is important to have UseShellExecute set to true.
Use the code together
Since we now have implemented both IViewRenderService and IHtmlToPdfConverter we can start using them by first register them in the Startup.cs file where your ConfigureServices method should be located (services.AddScoped<IViewRenderService, ViewRenderService>() and services.AddScoped<IHtmlToPdfConverter, HtmlToPdfConverter>()). Now lets see the code wrapped up together:
private readonly IViewRenderService viewRenderService;
private readonly IHtmlToPdfConverter htmlToPdfConverter;
public DashboardController(
IViewRenderService viewRenderService,
IHtmlToPdfConverter htmlToPdfConverter)
{
this.viewRenderService = viewRenderService;
this.htmlToPdfConverter = htmlToPdfConverter;
}
[HttpGet]
public async Task<IActionResult> GetPdf(SomeInputModel input)
{
var model = this.GetViewModel(input);
var htmlData = await this.viewRenderService.RenderToStringAsync("~/Views/Dashboard/GetPdf.cshtml", model);
var fileContents = this.htmlToPdfConverter.Convert(htmlData);
return this.File(fileContents, "application/pdf");
}
Since ASP.NET MVC has no built-in PDF functionality, the only way to convert a Razor view to PDF without a third party tool would be to write the conversion code yourself. This would be a massive undertaking and almost certainly not worth the effort. I would start by purchasing the ISO 32000-1 reference document and learning everything I could about how the PDF format works. At the time of this answer, the cost is around 200 Swiss francs.
MVC4 - even if it is the name of your Frameworks should be understood as the pattern called Model-View-Controller (MVC). The Idea of this pattern is to separate the these three components in order to replace them with different channels whenever reqeuired.
In your case, the Razor Template is a tool to generate a VIEW in HTML. Razor is limited to HTML - your pattern isn't. By design of MVC you can use any other tool to replace the VIEW from a HTML to a PDF, XML or whatever you desire.
what you should be looking for is a way, to use your existing MODEL (not VIEW) and generate a PDF output, using any library needed.
Perhaps I'm not calling RazorEngine in the correct place.
In my controller action I use the following code to call RazorEngine. But I think this may not be correct as when it calls through to .Execute() and then into MVC's GetActionCache() the HttpContextBase.Items fails with a "method not implemented" exception.
Am I calling RazorEngine in the wrong way? #Html.LabelFor() works fine.
string template = "#Html.EditorFor(model => model.OldPassword)";
string result = string.Empty;
var config = new RazorEngine.Configuration.TemplateServiceConfiguration
{
BaseTemplateType = typeof(System.Web.Mvc.Helpers.HtmlTemplateBase<>)
};
using (var service = new RazorEngine.Templating.TemplateService(config))
{
// Use template service.
RazorEngine.Razor.SetTemplateService(service);
result = RazorEngine.Razor.Parse(template, model);
}
powercat97 over on the github issues page has a workaround for an issue that addresses this.
https://github.com/Antaris/RazorEngine/issues/46
The reason I've had much trouble is that there is no context set. Creating a new ViewContext is not sufficient.
Therefore by calling a view that in turn calls our RazorEngine code via RenderAction() we get the context and the MVC framework has everything it needs when it is called by RazorEngine.
Using the AccountController as an example (HtmlTemplateBase comes from RazorEngine issues with #Html and http://www.haiders.net/post/HtmlTemplateBase.aspx):
public ActionResult Test()
{
var model = new MySite.Models.LocalPasswordModel();
model.OldPassword = "MyOldPwd";
model.NewPassword = "SomeNewPwd";
return PartialView(model);
}
[ChildActionOnly()]
public string TestTemplate(MySite.Models.LocalPasswordModel vm)
{
string result = string.Empty;
string template = "#Html.EditorFor(model => model.OldPassword)";
var config = new RazorEngine.Configuration.TemplateServiceConfiguration
{
BaseTemplateType = typeof(HtmlTemplateBase<>)
};
using (var service = new RazorEngine.Templating.TemplateService(config))
{
// Use template service.
RazorEngine.Razor.SetTemplateService(service);
result = RazorEngine.Razor.Parse(template, vm, "MyTemplateName");
}
return result;
}
and in Test.cshtml:
#model TestRazorEngine.Models.LocalPasswordModel
#{ Html.RenderAction("TestTemplate", new { vm = Model }); }
I have never worked with actionfilter so i dont really know how to use it, ive done som reseach but i dont completly understand it. But basicly im going to create a new controller, and i want my _Viewstart.cshtml to use this controller. The problem is that i dont know how to use this code to an actionfilter and then call this controller in _viewstart.
The code that i want in my controller is.
var TemplateIDSession = Session["TemplateID"];
if (TemplateIDSession != null)
{
int tempID = (int)TemplateIDSession;
var template = servicetemp.GetEntry(tempID);
var servicetemp = ServiceFactory.Instance.CreateTemplateService();
Response.ContentType = "text/css";
return RazorEngine.Razor.Parse(System.IO.File.ReadAllText(Server.MapPath("Content/Site.css")));
I think you should go about this in a different way, by using a HTML Helper for the CSS, like so:
public static class Helpers
{
public static string OrganizationStyleTemplate(this HtmlHelper html)
{
TagBuilder tagBuilder = new TagBuilder("style");
var templateIDSession = HttpContext.Current.Session["TemplateID"];
if (TemplateIDSession != null)
{
// retrieve your css from the database and insert it into the tag
tagBuilder.InnerHtml = dbObject.CSSYouveStored;
}
return tagBuilder.ToString(TagRenderMode.Normal);
}
}
Then usage would be like so:
#Html.OrganizationStyleTemplate()
P.S. If you need to analyze if the user is authenticated within that method, use:
HttpContext.Current.Request.IsAuthenticated
Would it be a good idea, and executable, to use the ASP.NET MVC View Engine to render html to be sent out by email?
I know it's possible to let the view render into a string. So that could be use to build the mail message.
Since ASP.NET MVC is already used in the application, I get to use all practical ASP.NET MVC stuff without having to use Brail or NVelocity for my "mail views".
Good idea? Any caveats? Examples :) ?
Yes it is a good idea and relatively easy to implement.
I personally think it's a good idea. Definitely better than putting a piece of markup with placeholders into the database.
The disadvantage is that you will need Visual Studio to edit those templates then recompile and redeploy the project. You wouldn't be able to "outsource" working with templates to other non-technical staff.
And yes, adding new templates would also require your personal intervention.
Here,s my version of the RenderPartialToString as an extension method (which also takes care of paths etc..):
public static class ExtensionMethods
{
public static string RenderPartialToString(this ControllerBase controller, string partialName, object model)
{
var vd = new ViewDataDictionary(controller.ViewData);
var vp = new ViewPage
{
ViewData = vd,
ViewContext = new ViewContext(),
Url = new UrlHelper(controller.ControllerContext.RequestContext)
};
ViewEngineResult result = ViewEngines
.Engines
.FindPartialView(controller.ControllerContext, partialName);
if (result.View == null)
{
throw new InvalidOperationException(
string.Format("The partial view '{0}' could not be found", partialName));
}
var partialPath = ((WebFormView)result.View).ViewPath;
vp.ViewData.Model = model;
Control control = vp.LoadControl(partialPath);
vp.Controls.Add(control);
var sb = new StringBuilder();
using (var sw = new StringWriter(sb))
{
using (var tw = new HtmlTextWriter(sw))
{
vp.RenderControl(tw);
}
}
return sb.ToString();
}
}
usage:
return this.RenderPartialToString("YourPartialView", yourModel);
hope this helps..
jim
You can use MVCMailer NuGet - it uses the MVC view templates and you just write a single line of code to do this!