Creating MVC3 Razor Helper like Helper.BeginForm()
says that it can be done using extension methods and implementing IDisposable. Can the same be done by using declarative Razor helpers eg. #helper SomeHelper(){}?
Sort of.
Razor helpers return raw HTML, not IDisposable, so you can't use it with using.
However, you can create a Razor helper in App_Code to render the content, then call it from a normal extension method that writes the content directly to the page and returns a separate IDisposable.
No because helper.BeginForm() requires the IDisposable method to write out the closing </form> tag. As a razor helper is essentially a method and not a class it can't implement IDisposable.
Related
I am reading a book about ASP.NET MVC using Razor syntax and got confused about some codes that in the book. Just wondering what does that mean
#using(Html.BeginForm("AddToCart", "Cart")) {....})
Why use "using" key word here? Can anyone explain to me a little bit, thx.
in this scenario, razor will generate following code in HTML
<form action="/Cart/AddToCart" method="post">
</form>
now with the "using" statement, there are two purpose:
to import the namespace
declare the variable in the using statement will call iDisposable method when it goes out from the close bracket.
In the above scenario it is just a indication of when to open the form tag and close tag.
ref: http://msdn.microsoft.com/en-us/library/yh598w02.aspx
When using this syntax, closing form tag is rendered at the end of using statement automatically.
You can check the documentation here
BeginForm Method
Manual http://msdn.microsoft.com/en-us/library/dd460542(v=vs.108).aspx
You can use this method in a using block. In that case, the method renders the closing tag at the end of the using block.
The using statement makes sure to call the Dispose method of an IDisposable interface.
public static MvcForm BeginForm(this HtmlHelper htmlHelper)
MvcForm implements IDisposable such that it calls EndForm internally. EndForm closes the form tag and injects any validation fields or required JavaScript.
Is it possible to create EditorFor templates for a custom object using code only rather than a View template in the EditorTemplates.
My reason is so that I can create a class library with these templates.
Is it possible to create EditorFor templates for a custom object using
code only rather than a View template in the EditorTemplates.
Not unless you write your custom EditorFor helper. The standard helper looks for templates.
My reason is so that I can create a class library with these templates
In this case you could embed your templates into an assembly as resources.
How can define a custom block like #for in Razor view? I read about #helper here and here also there is a similar question here but #helper method just define html tags at first then when you want to use in views just can pass some parameters, in other hand #for block is that I want, in views you can pass Html (with intelligence support), Does any one have any idea about this? I also think about modify razor source code! (if possible) Is there any better way?
You may take a look at Razor Templated Delegates.
Ok, this is for me a very tough challenge. We're taking our existing ASP.NET website and converting (redesigning the PL only) to MVC. Our site is very complex. But the hard part is to convert the existing custom controls to MVC equivilant. The custom controls (I am not talking about user controls) are just of course a class currently that inherits System.Web.UI.Control and uses that object throughout. For example, we have some properties at the top of this existing custom class like so:
Dictionary<int, Control> configControls;
DropDownList kControl;
CheckBox confirmBox;
These all are variables of type Web controls in classic ASP.NET.
So I figured maybe what I could do (without building entire new custom controls from scratch) is to use the HtmlHelper object. So I tried this:
(include first the using statement that includes System.Web.MVC.Html at the top of my new custom class in our new web project)
private HtmlHelper helper;
Dictionary configControls;
helper.DropDownList
but this is not working. I guess I can't use this object just like this ?? I figured I can use HtmlHelper in the Dictionary and then make variable types off of helper. but those are just extension methods, not objects
I don't know of an equivalent to something like the generic "Control" we had available to us to inherit from such as in classic ASP.NET. Surely it won't be the same in MVC obviusly (stateless and a completely diff way of doing things) but what can I use in MVC with the same concept sort of?
So I figured maybe what I could do (without building entire new custom controls from scratch) is to use the HtmlHelper object. So I tried this:
(include first the using statement that includes System.Web.MVC.Html at the top of my new custom class in our new web project)
private HtmlHelper helper;
Dictionary configControls;
helper.DropDownList
but this is not working. I don't even know if this approach will work in my custom control. And when I try to use my helper variable, I get no extension methods unless it's inside an existing extension method where the signature has an HtmlHelper param passed in. So when I create that private variable just in my custom class outside, I get nothing in intellisense to choose from when doing "helper.". So do I need to define that object like this: ?
private HtmlHelper htmlHelper = new HtmlHelper();
but it's asking for a ViewContext and an IViewDataContainer as params. If I'm building out a custom method that knows nothing yet about its view (it shouldn't need to) because I'm simply creating strings of HMTL in this custom class to be passed to the Extension method to ultimately spit out fields then maybe I can't use HtmlHelper this way in a custom class like this.
So can I use that object in a way instead of "Control"? Maybe I can even in my dictionary variable use type object in place of control ? I don't know and then cast object to type HtmlHelper when I need to use or reference that value from the dictionary? But for now, I figured I can use HtmlHelper object in the Dictionary and then make variable types off of helper. but those are just extension methods, not objects.
I hope I am making any sense here when you read this.
I just blogged about this last night, some of this might be helpful for you.
WebForms And MVC In Harmony — Almost…
Basically it discusses some options for emulating "WebControls" using MVC.
Additionally, you can still use WebControls like you could before (granted they may not work if they need things like the ViewState). The problem I've discovered with that is you have a disconnect from the inline render code and the WebControls themselves.
I did write this method last night which let you use WebControls with inline code.
using System.Reflection;
using System.IO;
using System.Web.UI;
using System.Web;
using System.Web.Mvc;
public static class MyExtensionMethods {
//example method - renders a webcontrol to the page
public static void RenderControl(this HtmlHelper helper, Control control) {
//perform databinding if needed
MethodInfo bind = control.GetType().GetMethod("DataBind");
if (bind is System.Reflection.MethodInfo) {
bind.Invoke(control, null);
}
//render the HTML for this control
StringWriter writer = new StringWriter();
HtmlTextWriter html = new HtmlTextWriter(writer);
control.RenderControl(html);
//write the output
HttpContext.Current.Response.Write(writer.ToString());
//and cleanup the writers
html.Dispose();
writer.Dispose();
}
}
//then used like...
<% int[] numbers = { 1, 2, 3, 4, 5 }; %>
<% this.Html.RenderControl(new DataGrid() { DataSource = numbers }); %>
Just an interesting concept you might be interested in.
Short of hacking webforms controls into your MVC application, servercontrols with many methods do not map to MVC.
They are replaced by partials and controllers(or subcontrollers if you like that sort of thing).
If all you want to do is render some HTML based on a few parameters, then a Helper is what you are after. Static Class, static methods. If however, you need to keep state, and do a bunch of stateful stuff, then a partial, JS, and controller(or subcontroller) are really what you are after.
Server Controls that manage their own state really are a thing of the past in MVC.
Remember that MVC is an attempt to use the web the way it was meant to work, particularly if you bring REST into the picture. Webforms is a fudge to make the web work like windows forms.
I would create needed business logic, shared partial view (probably, with quite a lot of well structured javascript lines attached) and seperated controller.
Then i would use this bunch of code through partial request technique.
Not sure how much this will be of help but, do have a look at this series of blog post
Custom controls everywhere
Also have a look at the Catharsis project
Web-Application Framework - Catharsis - Part I - New Solution
The codeplex URL for the same is
Catharsis
This project has some good examples of control creating for asp.net mvc.
I make heavy use of View Components in some of the larger applications I've built in Monorail - What is the equivalent approach in ASP.Net MVC for a view component, that can support sections etc.?
Actually you have several options to create the equivalent of a ViewComponent in ASP.NET MVC, depending in the complexity of your component. I use these two approaches which are the more mvc-ish of the options I am aware of.
1:
The simplest thing is to create a ViewUserControl and display it using Html.RenderPartial with the helper. The ViewUserControl is a simple piece of markup with no backing controller (I think you can put a codebehind file if you want).
Optionally, you can pass a model object or the entire ViewData dictionary to the view when calling RenderPartial, like this:
<% Html.RenderPartial("TopBar", model); %>
"TopBar" is an ascx page. This works anywhere, in master pages and in normal views.
2:
If you want your component to have more complicated logic or to access datasources, IoC, etc, then you can use Html.RenderAction which is an extension method found in the Microsoft.Web.Mvc assembly. I am using this out of the mvccontrib distribution. It works like this, you need to create a normal controller with all the logic you need, then create some views and all of these things become your component, for example:
public class AboutComponentController : Controller {
public IRepository Repository{ get; set; }
public ActionResult Detail() {
var lastEvent = Repository.FindAll<Auditoria>().FirstOrDefault();
return View(lastEvent);
}
}
Notice how I have a reference to an IRepository which is going to be injected with IoC (Windsor in my case) and I can do anything a normal controller would do.
Now, in any page (master or normal) where you want to use your component, import Microsoft.Web.Mvc and call Html.RenderAction with the appropriate parameters. This will create a mini mvc pipeline that creates the controller, resolves the view, etc., just like a Monorail ViewComponent. I prefer to use the lambda based variation of the method, like this:
<% Html.RenderAction<AboutComponentController>(x => x.Detail("a message"));%>
Unfortunately, the only way to pass parameters is to use the method call itself, which in turn must be unique in the controller. Still needs some work to resemble a ViewComponent.
I don't use masterpages or layouts in the views of my components since they are composition elements themselves.
Remember that when using the Webforms view engine, you can have strongly typed views if you like to have intellisense when using the Model variable in code blocks.
The beauty of this is that you can mix view engines with these approaches, I usually create the components in nvelocity and display them in aspx pages, etc.
I now there can be issues with caching of the partial views but I haven't run into any so far. I am sure there are other options (like subcontrollers in mvccontrib) but this is usually enough for simple cases. Of course you can use normal ASP.net components in your aspx view pages but that would be cheating right? hehe. I hope it helps.
Phil Haack blogged about creating areas to group controllers into sub-folders/sections similar to MonoRails.