I want to render a form used to create a new instance of a Model. I tried,
#Html.EditorFor(model => new Person())
But I got the error,
Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions.
I tried,
#Html.EditorForModel("MyNamespace.Person")
but nothing rendered. How do I use Html.EditorFor when I dont have a model instance to pass to it?
It seems that you're a bit confused about how to use #Html.EditorFor(). First,, your use of the lambda expression doesn't quite make sense, model => new Person(). If you want to create a new instance of a model then there's no need to use a lambda, just new Person() gives you that instance.
Second, you don't need an actual instance to pass into #Html.EditorFor(). The purpose of this method is to produce an html markup including an input field for a property or even multiple properties.
So let's say your Person model had an Age property, then you can create an edit field for that attribute by calling
#Html.EditorFor(model => model.Age)
Now where does model come from? You have to define it in your view, so add this line to the top of your view file so that ASP.net knows which model to grab the Age attribute from,
#model <namespace>.Models.Person
The namespace is usually the name of your project, and if you don't put your models in the Models folder, then replace that with where ever your model is contained in.
Related
I am working on an ASP.NET MVC-4 web application. I'm defining the following inside my action method to build a SelectList:
ViewBag.CustomerID = new SelectList(db.CustomerSyncs, "CustomerID", "Name");
Then I am rendering my DropDownListFor as follow inside my View:
#Html.DropDownListFor(model => model.CustomerID, (SelectList)ViewBag.CustomerID, "please select")
As shown I am naming the ViewBag property to be equal to the Model property name which is CustomerID. From my own testing, defining the same name didn't cause any problem or conflict but should I avoid this ?
You should not use the same name for the model property and the ViewBag property (and ideally you should not be using ViewBag at all, but rather a view model with a IEnumerable<SelectListItem> property).
When using #Html.DropDownListFor(m => m.CustomerId, ....) the first "Please Select" option will always be selected even if the value of the model property has been set and matches one of the options. The reason is that the method first generates a new IEnumerable<SelectListItem> based on the one you have supplied in order to set the value of the Selected property. In order to set the Selected property, it reads the value of CustomerID from ViewData, and the first one it finds is "IEnumerable<SelectListItem>" (not the value of the model property) and cannot match that string with any of your options, so the first option is selected (because something has to be).
When using #Html.DropDownList("CustomerId", ....), no data-val-* attributes will be generated and you will not get any client side validation
Refer this DotNetFiddle showing a comparison of possible use cases. Only by using different names for the model property and the ViewBag property will it all work correctly.
There is not harm to use it. You will not get any error. but best practice is to bind model property.
How to access Model property(Like #Html.EditorFor(x=>Model.Name)) in Razor view of IEnumerable Type without using Loops??I.e If a view is strongly typed to some Model holding Model as a LIST.Eg.
#model IEnumerable<EFTest2.DAL.package_master>
Then is it possible to Display TestBoxFor or EditorFor (to create new Model) Html helper without using foreach Loop.???
When some model property is of type IEnumerable<SomeType> you would normally define an editor/display template (~/Views/Shared/EditorTemplates/SomeType.cshtml or ~/Views/Shared/DisplayTemplates/SomeType.cshtml). This template will be automatically rendered for each element of the collection so that you don't need to write loops:
#Html.EditorFor(x => x.SomeCollection)
and inside the template you will be able to access individual properties:
#model SomeType
#Html.EditorFor(x => x.Name)
...
Now, if you absolutely need to directly access some element inside a view which is strongly typed to IEnumerable<SomeType> you would better use some other collection type such as IList<SomeType> or SomeType[] as view model which will give you direct access to elements by index and you will be able to do this for example to access the 6th element of the collection:
#model IList<SomeType>
#Html.EditorFor(x => x[5].Name)
So basically you are mentioning of type List etc.
If you want to add values to the list accepting input from user from form fields and then add to the existing list in model. the easiest but not so elegant way would be
suppose you have class "Person" and then List in your model. first create an instance of person that will have empty person instance , add it to list and then bind this last list item to your edit for.
#{
Person contact = new Person(); //Empty person instance
PersonList.Add(contact);
}
later on bind this to your induvidual fields
#Html.TextBoxFor(m => m.PersonList[PersonList.Count - 1].PrimaryContacts.FirstName)
This works good for Validation on model properties as-well and also after every form submit, for next inclusion you just add the new person. but take care to write the remove peice of code if form is cancelled.
I have an insurance entry form that has contact information for two people. I have created a Razor partial view for the contact entry and put it in the form twice. The 'master' view model (VmApplicationForm) contains two instances of a subsidiary view model (VmPolicyHolder) corresponding to the two contacts as well as some properties common to both contacts. I am calling #Html.RenderPartial("_CreateOrEdit", Model.contactInfo1) and #Html.RenderPartial("_CreateOrEdit", Model.contactInfo2) in the page. With this arrangement (no surprises) the rendered code has duplicate IDs for the form input elements.
Is there any way of getting RenderPartial to prefix the IDs and Name attributes? I couldn't see this in the documentation, but perhaps I've missed something.
Sorry, I don't have time yet to give you the example code, but i'll give you the idea. You should first create EditorTemplate for that probably called ContactInfo class. And then, in the base class(Holding that two contacts) edit view, you should write
#Html.EditorFor(model => model.contactInfo1)
#Html.EditorFor(model => model.contactInfo2)
This way, it will render that EditorTemplate and generate correct ids and names to inputs within it.
What you are doing is trying to post a collection of items in a form- this can indeed be done in MVC (as well as in any web page/application that uses a FORM tag), however it requires some special handling to avoid id collisions and to correctly format the post data. Steve Sanderson has a great post on how to accomplish this:
http://blog.stevensanderson.com/2010/01/28/editing-a-variable-length-list-aspnet-mvc-2-style/
Essentially its a wrapper to append unique guids to element ids (in your case for each contactInfo), and create the proper array format in the tags. eg <input name="ContactInfo[f2cc4d6b-fc32-45e9-9d3d-fce54c3fede3].FirstName">
if your model is something like ContactInfo, you will end up posting like
[HttpPost]
public ActionResult Index(IEnumerable<ContactInfo> contacts)
{
// To do: do whatever you want with the data
}
I have a view with a form that's is typed to a viewmodel called AddEditItemVM. This viewmodel has the following property:
public List<Category> Categories{get;set;}
What im trying is two things:
Render a checkbox foreach Category in the generic category list of my viewmodel.
Make that when the form is posted receive, in my controller action, the property Categories instantiated (into the instance of AddEditItemVM)
About the first point, i would like to use any helper (if exists) that renders a group of checkboxes using lambda expressions like (m=>m.Categories), instead to render the checkbox with a foreach into the view.
About the second point, i read that there is one feature in MVC called Custom Model Binders. These get values from ValueProviders (querystring, cookies, or Form values) and creates the necessary instances passing it to specific action called after a form was posted. Should i create one custom model binder in order to receive my property Categories instantiated?
This might work
CheckboxList in MVC3.0
I am using MVC 3 w/ Razor and using the new dynamic ViewBag property. I would like to use the ViewBag property with the EditorFor/LabelFor Html helpers but can't figure out the syntax.
The View does have a #model set, but the object I am trying to use is not part of that model. I am aware I can create a ViewModel but that is not what I am after.
Can anyone help?
Controller:
var myModel= _repo.GetModel(id);
var newComment = new Comment();
ViewBag.NewComment = newComment;
return View(myModel);
View:
#model Models.MyModel
#(Html.EditorFor(ViewBag.NewComment.Comment))
I haven't tried it, but this should work I think.
#(EditorFor(m => ViewBag.NewComment)
It is possible to use a Linq-to-SQL syntax, but use a completely different object on the right side.
Not knowing what your Comment Model looks like, my gut reaction would be to just do:
#Html.EditorFor(ViewBag.NewComment)
However, because ViewBag is dynamic, you may need to cast NewComment before you use it, in order to get the EditorFor magic.
#Html.EditorFor(ViewBag.NewComment as Comment)
Update
Strike that, EditorFor can only accept an Expression as a parameter, and that Expression must return a property of the page model. I don't think EditorFor or EditorForModel are going to be of any use to you if you don't want to use a ViewModel. Have you considered switching the roles of whatever it is you're using the Model for, with that of the ViewBag?
If for some reason I need to use ViewData to pass the model into my view I do the following to allow for the Html.DisplayFor() helpers.
In the views code block I cast the ViewData model object to its underlying type
var newCommentModel = ( NewComment )ViewBag.NewComment;
Then I assign the following expression to the helper using the strong-typed reference
#Html.DisplayFor( model => newCommentModel )
The expression tree now contains a strongly-typed model and the DisplayTemplate is correctly displayed.