I'm going to write a ton of helpers for my app.
For many of them I'd like not to extend HtmlHelper, but to create another helper class instead, for two reasons: 1) to be able to write, say, Link.Home and Icon.Edit instead of Html.HomeLink and Html.IconEdit; 2) to be able to easily tell standard helpers from custom ones and where the latter are defined.
Is this possible? How?
Is this not recommended? why?
thanks
Well, "helper methods" are just extension methods. If you want to be able to write Link.Home in your views, you'll have to extend ViewPage and add property called Link of type, say, ILink. The ILink interface may itself be empty. Now all your views should inherit from MyViewPage and writing helper methods becomes a simple task:
public static string Home(this ILink link, string text)
{
// ...
}
This would be possible by subclassing HtmlHelper and calling the new class Link and Icon for example.
I would not recommend it for the simple reason that Html.HomeLink and Html.IconEdit clearly states what the method does, it outputs Html in the form of a HomeLink and and an Edit Icon.
Related
I am building an application using Play for Model and Controller, but using backbone.js, and client side templating. Now, I want the html templates to be served by Play without any backing controller. I know I could put my templates in the public directory, but I would like to use Play's templating engine for putting in the strings in my template from the message file. I do not need any other data, and hence dont want the pain of creating a dummy controller for each template. Can I do this with Play?
You could create a single controller and pass in the template name as a parameter, but I am not sure if it is a good idea.
public static void controller(String templateName) {
// add whatever logic is needed here
renderTemplate("Controller/"+templateName+".html");
}
Then point all your routes to that controller method. Forget about reverse routing, though.
I think I would still rather have a separate controller method for each template. Remember that you can use the #Before annotation (see Play Framework documentation) to have the message string handling in exactly one place, that is executed before each controller method. By using the #With annotation you can even have this logic in a separate class.
You can use template engine from any place in your code:
String result = TemplateLoader.load("Folder/template.html").render(data);
I have found a dozens of threads about getting the name of the controller and method based on the url, I managed that just as well. Can I get the MethodInfo of the method based on their name automatically from the MVC engine, or do I have to do Type.GetType("Namespace.Controllers."+cname+"Controller").GetMethod(mname)? Which is not so nice, since how do I know the namespace in a framework class? How do I know if the default naming patterns are being observed, or is there a different config in use?
I want to get a "What Would MVC execute?" kind of result....
Is it possible?
EDIT: further info:
I have a framework which uses translatable, data-driven urls, and has a custom url rewriting in place. Now it works perfectly when I want to show the url of a news object, I just write #Url.Content("~/"+#Model.Link), and it displays "SomeNewsCategory/SomeNews" instead of "News/29" in the url, without the need to change the RouteTable.Routes dynamically. However in turn there is a problem when I try to write RedirectToAction("SomeStaticPage","Contact"); into a controller. For that, I need to register a static link in db, have it target "/SomeStaticPage/Contact", and then write
Redirect("~/"+DB.Load(linkid).Link); and that's just not nice, when I have 30 of these IDs. The web programmer guy in the team started registering "fake urls", which looked like this:
public class FakeURL
{
public string Controller;
public string Action;
public int LinkID;
}
and then he used it like Redirect(GetFakeUrl("controller","action")); which did the trick, but still was not nice. Now it got me thinking, if I apply a [Link(linkid)] attribute to each statically linked method, then override the RedirectToAction method in the base controller, and when he writes ReturnToAction("action","controller"), I'll actually look up the attribute, load the url, etc. But I'm yet to find a way to get the methodInfo based on the names of the controller and the action, or their url.
EDIT: I've written the reflection by myself, the only thing missing is getting my application's assembly from inside a razor helper, because the CallingAssembly is the dinamically compiled assembly of the .cshtml, not my WebApplication. Can I somehow get that?
To answer your edit, you can write typeof(SomeType).Assembly, where SomeType is any type defined in code in the project (eg, MvcApplication, or any model or controller)
Also, you can write ControllerContext.Controller.GetType() (or ViewContext) to get the controller type of the current request EDIT That's not what you're trying to do.
I found out that it was totally wrong approach. I tried to find the type of the controller based on the name, when instead I had the type all along.
So instead of #Url.Action("SomeAction","SomeController") I'll use #Url.MyAction((SomeController c)=>c.SomeAction()), so I won't even have to find the controller.
I would like to create an extension helper with the following signature:
public static MvcHtmlString
BindMissingFor(this HtmlHelper
htmlHelper, Expression> expression )
I would like this method to reflect through the supplied expression model and look for bind-able properties that have not already been bound on the form.
The use case is I would like to have some Views that only allow the user to interact with a portion of my Model. But, I would like to persist the entire model between multiple views (a wizard).
My current solution is to use a hidden-input for each field I don't want displayed. I'll probably do the same thing with this extension method, but I would like it to do the work for me instead of copy/pasting.
Is there a way to inspect the current form for inputs/selects from within an HtmlHelper extension method?
There is no way an html helper to know what happens in other parts of your view such as inspecting other form fields unless you pass it as argument. Also it is not very clear what you mean by look for bind-able properties that have not already been bound on the form. For persisting state in a wizard you might take a look at the Html.Serialize helper currently situated in the MVC Futures assembly. The idea behind this helper is that it allows you to serialize some model object (marked as [Serializable]) as hidden field inside a form and get its value back in a controller action using the [Deserialize] attribute. Behind the scenes it uses WebForms ViewState. You can also encrypt it. It is a good way of persisting state on the client between multiple pages.
Sorry if this is a basic question - I'm having some trouble making the mental transition to ASP.NET MVC from the page framework.
In the page framework, I often use ASCX files to create small, encapsulated chunks of functionality which get inclded in various places throughout a site. If I'm building a page and I need one of these controls - I just add a reference and everything just works.
As far as I can tell, in MVC, the ASCX file is just a partial view. Does this mean that wherever I want to add one of these units of functionality I also have to add some code to the controller's action method to make sure the relevant ViewData is available to the ASCX?
If this is the case, it seems like a bit of a step backwards to me. It means, for example, that I couldn't just 'drop' a control into a master page without having to add code to every controller whose views use that master page!
I suspect I'm missing something - any help would be appreciated.
Thanks,
- Chris
As far as I can tell, in MVC, the ASCX
file is just a partial view. Does this
mean that wherever I want to add one
of these units of functionality I also
have to add some code to the
controller's action method to make
sure the relevant ViewData is
available to the ASCX?
Yes.
However, you can use a RenderAction method in your view instead of RenderPartial, and all of your functionality (including the data being passed to the sub-view) will be encapsulated.
In other words, this will create a little package that incorporates a controller method, view data, and a partial view, which can be called with one line of code from within your main view.
Your question has been answered already, but just for sake of completeness, there's another option you might find attractive sometimes.
Have you seen how "controls" are masked on ASP.NET MVC? They are methods of the "HtmlHelper". If you want a textbox bound to "FirstName", for example, you can do:
<%= Html.Textbox("FirstName") %>
And you have things like that for many standard controls.
What you can do is create your own methods like that. To create your own method, you have to create an extension method on the HtmlHelper class, like this:
public static class HtmlHelperExtensions
{
public static string Bold(this HtmlHelper html, string text)
{
return "<b>" + text + "</b>\n";
}
}
Then in your view, after opening the namespace containing this class definition, you can use it like this:
<%= Html.Bold("This text will be in bold-face!") %>
Well, this is not particularly useful. But you can do very interesting things. One I use quite often is a method that takes an enumeration and created a Drop Down List with the values from this enumeration (ex: enum Gender { Male, Female }, and in the view something like Gender: <%= Html.EnumDropDown(Model.Gender) %>).
Good luck!
You can render a partial view and pass a model object to.
<% Html.RenderPartial("MyPartial", ViewData["SomeObject"]);
In your partial view (.ascx) file, you can then use the "Model" object (assuming you've inherited the proper object in your # Control deceleration) to do whatever you need to with that object.
You can, ofcourse, not pass and Model and just take the partial view's text and place it where you want it.
In your main view (.aspx file), you will need to define the proper object in the ViewData that you're passing to the partial view.
Another method you can do is use:
<% Html.RenderAction("MyAction", "MyController", new { Parameter1="Value1"}) %>
What the previous method does is call a controller Action, take its response, and place it where you called the "RenderAction()" method. Its the equivalent of running a request against a controller action and reading the response, except you place the response in another file.
Google "renderaction and renderpartial" for some more information.
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.