I have 2 Cotrollers.
First one sets the ViewData property like this
ViewData["Error"] = "something";
I am able display this message on the page.
Second Controller loads the grid.
When i try to set the ViewData property from that Cotroller, It does not show up on the page.
Do you why? Am I doing anything wrong here?
Please let me know.
Thanks!!!!
Using two controllers for a single view is a bit of a no-no.
Look into ViewModels to pass all of the required data to your view. You can then create a PartialView for your grid, and pass the necessary model to the Partial View as well. Consider ViewData / ViewBag a last resort when a ViewModel doesn't work.
Are you trying to use two separate controllers to render the same view? If so you should probably consider, breaking the view logic of your "grid" into a partial view that you in turn render within your primary view.
As you mentioned "ViewData" twice, another item for consideration is the implementation of the ViewModel Pattern. The Viewdata dictionary approach is fast and fairly easy to implement. however, it is not type-safe and errors due to typo's will not be caught at compile time.
Related
I'm working on some forms, and often I can reuse the same amount and combination of fields together, is it possible to group them all as a template and then call it from the page?
For example:
2 radio buttons with labels and 2 texboxes under.
How is it called so i can do a proper research?
You can use Partial View, its like a reusable component.
These links will elaborate more:
http://www.devcurry.com/2012/04/partial-views-in-aspnet-mvc-3.html
http://www.dotnet-tricks.com/Tutorial/mvc/2IKW160912-Partial-View-in-Asp.net-MVC3-Razor.html
MVC3 Partial Views
Create a Partial View and keep your markup which you want to reuse in that. You can use these Partial views in other views as needed then.
You can use the Html.Partial helper method to call the partial views in other views.
#Html.Partial("RecentItems")
You can also pass some model to your partial view as well
#Html.Partial("RecentItems", Model.RecentItems)
Assuming Your partial view is strongly typed to a class which is of the same type as the type of Model.RecentItems, of the caller view.
In cases where new items need to be added to a list via ajax, what is the biggest benefit of using something like Knockout.
So far what I have been doing is, on my view, use an editortemplate (with asscociated viewmodels) to render a list of items. Then to add a new item, I make a request to an action that loads a server-side viewmodel, and returns an EditorTemplte object which just gets appended to the list. Like this:
return Json(new { this.RenderPartialViewToString("MyEditorTemplate", model) });
The knockout way of doing things requires the implementation of another view model to display items, and then another template to display it. But doing it this way requires duplication of code since the view model has to be represented in 2 places: in the cserver side code and then the view for the knockout viewmodel. Isn't that bad practice?
Am I missing something, or understanding the purpose of knockout and MVVM?
The biggest benefit that you will see from Knockout is that you will not need to hit the server in order to add a new item to your list - everything happens client side. This has multiple benefits including:
You reduce load on your server.
You improve the end-user's experience.
You can keep multiple elements on the page up-to-date with your model without any server interactions.
Two great examples of this can be found at these Knockout tutorials:
Working with Lists and Collections
Loading and Saving Data
As far as duplicating code, if you take a look at those two tutorials, you'll notice that you don't need to duplicate code. For example:
Create a view to display your entire list.
To add a new item to the list, create a partial view that you load when you add a new item to the page - that partial view is bound to Knockout
When you submit the entire form, everything in that list will be submitted - including those items you added via Knockout.
Your ViewModel will be specific to your list item (you don't need to create an entire ViewModel for everything, necessarily). And your view is specific to a single list item.
Hope that's clear. Knockout is pretty straightforward and they have some great documentation and tutorials to help you move forward.
IMHO, the following is cleanest option for the architecture of knockout and asp mvc mixed together.
Have your ASP.net acting as a webservice and have knockout control all your view templating and logic.
Otherwise, yes there will be potential replication of viewmodels and having to refactor both front and backend code when you need to change your model.
I have created a base viewmodel that all of my view models inherit from. That part is easy.
All views are bound to a viewmodel (all are inherited from the base view model)
Within the OnActionExecuted method I insert a true/false value onto a property within the baseviewmodel depending on some conditions.
From the view side of things. I have a single layout page that some how I want to be able to read the property's value and render a different partial view based on the value.
Is this possible? I dont want to have to add the code to each of the views but I don't think I should be binding the layout to my baseviewmodel either.
If I can stay away from inserting the value into the valuebag that would be great as I need to be able to access these values anywhere in the application via strongly typed names.
what you want probably isnt possible because as you call a view from the controller then first the code inside that view is executed and then the layouts code is executed
to achieve what you are doing you can do 2 things
1. make the logic inside the controller itself and then render the correct view
2.call the layout from the controller giving it the name of the partial view in some property of the model or in the viewbag
Not sure I quite follow the use case, but rather than trying to render out a partial view, have you thought about nesting your layout pages.
I think you should be able to override the layout in the onactionexecuted, so you can set the layout dependant on the bool and that layout will render only the correct option.
Look here for an example:
Nested layout pages with Razor
HTH
Si
I'm trying to use a html.dropDownList helper with a strongly typed view model with ajax. I can't the post the code because of the nature of the project.
Here basically what I'm doing...
loading a mvc view via a strongly type view model
clicking a button which does an ajax post to a controller method
using the TryUpdateModel to parse the view model
processing the request
rendering a parital view for the ajax request
According to the article listed below, the problem is that "ASP.NET MVC assumes that if you’re rendering a View in response to an HTTP POST, and you’re using the Html Helpers, then you are most likely to be 'redisplaying a form' that has failed validation."
http://blogs.msdn.com/b/simonince/archive/2010/05/05/asp-net-mvc-s-html-helpers-render-the-wrong-value.aspx
Instead of "redisplaying the same form value", I need the html.dropDownList to be set to the same value in the view model.
Does anyone know of any custom dropDownList helpers or have any ideas of how to achieve this?
Things I've already tried/considered
per the blog, manually removing the modelstate item...didn't work - didn't pick up the value in the view model - just defaulted to the first item in dropdown list
considered just writing a regular select list...but this is sloppy and cumbersome since I'm rending multiple select lists in a loop
writing my own custom dropDownList helper...wanted to avoid reinventing the wheel
Thanks in advance
Its not fully clear to me what your problem exactly is, but I've had a similar problem. I used the Html.DropDownListFor(, SelectListItem[]) helper. At postback it sets the value to the choosen one. Your postback view doesn't require to have all the fields of the original model.
#Html.DropDownListFor(model => model.SelectedValue, MyModels.DropDownSelectables());
Here I want the selected value as the model.SelectedValue variable and within my (seperate) model I made a array of selectlistitems. The rest is automagic.
Hope it helps, D
I have a conditional business logic that determines whether a property from a model should be displayed in a view. according to best practices where would be the place to implement it?
Implementing this logic in the view level does not seem right to me.
Thanks
IMO, it is belonged to the Model. I would put that business logic in IsRequiredYourProperyName property in the model.
Really? I would have thought that would be fine in the view provided you're passing the boolean indicating whether or not it should be displayed as part of the ViewModel. The view shouldn't be querying an outside resource to see if it should render certain UI elements, but if everything it needs to determine what to render is in the ViewModel, what's wrong with a simple if{} statement? Alternatively if a conditional display property is common you could create a custom DisplayTemplate or EditorTemplate and for it and implement the logic there.
So your ViewModel should wrap everything you want to send to the view. in your case it sounds like it should wrap your DomainModel and some sort of dictionary or KeyValuePair collection detailing if each property should be displayed or not as booleans. That's what I would do anyway.