asp.net sending a List<> of items to controller - asp.net-mvc

I have the following form:
<li>
<% using (Html.BeginForm("TestMethod", "MyController", FormMethod.Post, new {id = "TestMethod"}))
{%>
<%= Html.Hidden("model", Model.MyListOfObjects) %>
<%}%>
Test
</li>
And the javascript function for the onclick is as follows:
function SubmitForm() {
document.forms["TestMethod"].submit();
}
I am trying to pass the list of objects from the view into the controller, but i have yet managed to get this to work. My Controller function is:
[Authorize]
[HttpPost]
public ActionResult TestMethod(List<Objects> model)
{
dynamic Expando = new ExpandoObject();
Expando.test = model;
return View(Expando );
}
When I view the List of objects in the debugger it always displays "System.Collections.Generic.List`1[]" with no actual objects inside.
So my question is what should I be doing to pass a List of objects into a controller?
I have also tried:
<% using (Html.BeginForm("TestMethod", "MyWork", FormMethod.Post, new {id = "TestMethod"}))
{%>
<% int itemx = 0; %>
<% foreach (var x in Model.MyListOfObjects)
{%>
<%= Html.Hidden("model"+"["+itemx+"]", x) %>
<%itemx++; %>
<% } %>
<%}%>

You cannot just put List<object> as action parameter and expect the model binder to be able to automagically guess what object types you want to put there. You will need to write a custom model binder if you wanted to handle multiple sub-types as illustrated in this post.
And if you want to use a single type for the list such as List<MyViewModel> then simply loop through each element of the list (respecting the convention) and for each element build a hidden field for each property that you want to bind.
But since those are hidden fields, I guess that the user is not supposed to modify them. In this case those hidden fields have nothing to do in your view. Let's not reinvent the ViewState that we were all so happy to get rid of when we moved to ASP.NET MVC from classic WebForms. Simply put a hidden field containing an unique id that will allow you to refetch the corresponding list elements in the POST action given this unique id from wherever you fetched them initially (your database or something I suppose).

You need to have one hidden element for each object in the list, and named model[0], model[1], etc.

Related

How to assign a dynamic value to the label helper in asp.net MVC

I am working on a Asp.net MVC 2.0 web application. In my form , i have non editable fields , so i wanted to display them as labels rather than textboxes.
I am strongly binding my model with view. So, i need to associate this label with one of the fields in model.
This is what i am trying to do:
<%=html.LabelFor(model=>model.changedby)%>
<%=html.DisplayFor(model=>model.changedby,XYZ)%>
But, it is displaying nothing..Please help
Updated2:
What basically i am trying to do is a add operation. i have a create view and that view has a form.
I am strongly binding this view with model.So , that i can directly associate form fields with the model Properties.
Ex:
<label> Name</label> <%=Html.TextBoxFor(m=>m.name)
So, what ever i type into the textbox , it will be stored in m.name in the model.
If the text entered is "Avinash" , then m.name gives value "Avinash"
I think i am correct upto this extent:
Similarly..
I have a field which is readonly , the user can not change the value of it.
<label>Changed On</label> <label> DateTime.Now </label>
How to bind m.ChangedOn with the labels values(DateTme.Now)
so that it will result in m.Changedon as DateTime.now
Updated3:
This is what i am writing..
<td >
<%=Html.LabelFor(Model=>Model.CreatedOn) %>:
</td>
<td>
<%=Html.HiddenFor(Model=>Model.CreatedOn) %>
</td>
You no need to wrap with <label>, since MVC LabelFor will automatically create those html tags for you
So change this
<label>
<%=html.LabelFor(model=>model.changedby)%>
</label>
to
<%= Html.LabelFor(model=>model.changedby) %>
Update:
If you want to send the data to the server while you post your form, make sure you have a data in a form fields. Only form fields like input,select,textarea are posted to server and not display tag value like label, span, div, etc
Still if you need to post the label value, you can use hidden with it
<%= Html.LabelFor(model=>model.changedby) %>
<%= Html.HiddenFor(model=>model.changedby) %>
If you have both, your hidden field will posted to server, which contains the same value
Controller code
public ActionResult Index()
{
MyviewModel model=new MyviewModel();
model.ChangedOn=DateTime.Now;
return View(model);
}
For Save
public ActionResult Save(MyviewModel model)
{
model.ChangedOn; // this property will show you hidden value
//If you need current time, since the rendered time was old. Its good to assign like below
//model.ChangedOn=DateTime.Now
}
use this
<%= Html.DisplayFor(model => model.changedby) %>

asp.net mvc ViewModel in a View with List of objects has old list items displayed after removing in controller

I have poked around but not found out what the ViewModel, or TempData or how my objects are being persisted for my form.
I display a custom view model in an asp.net MVC view, I edit a list of objects in that view and display them all inside a dynamic grid inside an html form, then submit the changes. When I get back to the controller I check existing objects vs the forms submitted object list and update the objects.
When I redisplay the form, objects that were deleted still show up and have values in the textbox inside the html elements, so it is asp popluating the fileds and not a browser cache. I have a checkbox that displays next to the row if it is an existing object already and those checkboxes are submitted to the controller as an array of values (the id of the object to remove).
So I delete the object, pull clean ones out of the database and set the list in the viewmodel with the newly retrieved data. However, the form shows the old object still, but there is no delete checkbox next to them so they were not retrieved from the database.
How do I fix that? I tried tweaking the methods output cache (not a browser issue as the DB ID key does not exists anymore ... no delete checkbox). I tried making a new view model an explicitly setting variables before sending to the view...no go.
My solution for now was to redirect to the get method after I edit all of the objects (simpleObject in the example) and start completely over.
A simplified example is as follows:
public class CustomViewModel {
List<SimpleObject> objects {get;set;}
}
public class SimpleObect {
public int iA {get;set;}
public int AddonHistID {get;set;}
}
Controller:
[HTTPGet] // get method and displays 2 objects by default
public ActionResult whatever( string something){
CustomViewModel form = new CustomViewModel ();
form.objects = new List<SimpleObject>();
form.objects.Add( new SimpleObect());
form.objects.Add( new SimpleObect());
return View( form)
}
[HttpPost]
public ActionResult whatever( string something, CustomViewModel form){
// adjust objects to show current objects aftering saving changes (reload and rebind to ModelView)
form.objects = getObjectsAfterChange( something); // just gets objects from db after all changes are made in this controller action
return View( form);
}
View:
<% using( Html.BeginForm()) { %>
<table width="800" id="SearchAddonsResults">
foreach( SimpleObject addonHist in Model.objects )
{
++iOdd;
string cssClass = (iOdd % 2 == 0 ? "rowOdd" : "rowEven");
%>
<tr class="<%= cssClass %>">
<td>
<%if (addonHist.AddonID > 0)
{ %>
<input type="checkbox" name="RemoveAddon" id="RemoveAddon" value="<%= addonHist.AddonID.ToString() %>" />
<% } %>
<%= addonHist.AddonHistID.ToString() %>
</td>
<td><%= addonHist.iA.ToString() %></td>
</tr>
<% } %>
</table>
<% }; //endform %>
I think this might help you get the results you expect.
Phil Haack's Blog:
http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx
Which is linked to from:
How to model bind to a List<ViewModel>?
Complex model binding to a list
How ASP.NET MVC: How can I bind a property of type List<T>?
So I delete the object, pull clean ones out of the database
and set the list in the viewmodel with the newly retrieved
data. However, the form shows the old object still,
This makes no sense. Are you absolutely sure that this line
form.objects = getObjectsAfterChange( something);
in your HttpPost method is retrieving the right information?
I would start by inspecting the value that getObjectsAfterChange( something) is returning . I suspect it's returning more than you think and that's where the problem is (rather than on the render of the view.)

ASP.NET MVC - Insert or Update view with IEnumerable model

I've seen plenty of examples (NerdDinner, Sanderson's Sports Store, etc.) where a view is bound to a collection of objects. The syntax in the view is usually something like this...
<%# Page... Inherits="System.Web.Mvc.ViewPage<IEnumerable<MyViewModel>>" %>
...
<% foreach (var myViewModel in Model) { %>
I've also seen plenty of examples of inserts or updates where the controller automatically binds the model parameter to the form elements in the view.
I'm looking for a mix of the two techniques where my view has form elements pertaining to a collection of myViewModels where each myViewModel has 3-4 properties. The intent is to allow the user to enter a set of these in one take.
Assuming this is possible, can anyone help me with the syntax? I can't figure out how to label the form elements to make the binding work.
This is possible through the built-in model binder, but you have to do a little bit of convention-based naming of your form objects. First, your action needs to take a collection:
[HttpPost]
public ActionResult CreateFoos(List<Foo> foos)
{
// I have a list of the foo objects that were posted
}
And then, in the view, let's say you wanted to make a form for each object:
<% for (int i = 0; i < Model.Count; i++) { %>
<%: Html.TextBoxFor(x => x[i].Property1) %>
<%: Html.TextBoxFor(x => x[i].Property2) %>
<%: Html.TextBoxFor(x => x[i].Property3) %>
<% } %>
Pay attention to how the controls are rendered in the HTML, because in your "create" view, you might want to have a javascript button that allows the user to add another record, and you'll have to increase the index for each additional control. It's not too hard, but I just wanted to warn you to pay attention to the source it actually generates.
The definitive answer is here: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx
You need to name each field as if it were part of an array: "PropertyName[i]"

ASP.NET MVC : How does my action result find the selected entry in a dropdownlist?

I have a dropdownlist that I populate with some stuff:
In my controller
ViewData["SourceModelList"] = new SelectList(_modelService.GetAllModels(), "Id", "Description");
in my view
<% using (Html.BeginForm("Compare", "Home")) { %>
<p>
<%=Html.DropDownList("SourceModelList")%>
</p>
<p>
<input type="submit" value="Compare" />
</p>
<% } %>
And this renders lovely. Now when I post back to my 'compare' action, how do I find out which item was selected in the drop down?
The name "SourceModelList" should correspond with the name of a field in your ViewModel, so that the binder has something to bind the value of the dropdown to.
Alternatively, you can pluck the value out of the FormCollection object, if your view is not strongly-typed.
The NerdDinner Tutorial goes into this process in greater detail:
NerdDinner Step 5: Create, Update, Delete Form Scenarios
http://nerddinnerbook.s3.amazonaws.com/Part5.htm
You can use any of the regular methods for getting items from a form in ASP.NET MVC: FormCollection, Request object, binding to a specific model or having an action which takes a string SourceModelList parameter.
You can do:
int value = Convert.ToInt32(Request.Form["SourceModelList"]);
Or by ModelBinders just making sure that your model have a property
public int SourceModelList {get; set;}
And the ModelBinder will get it for you.
Or, but less likely:
public ActionResult Name(FormCollection f, int SourceModelList)

ASP.NET MVC - Getting Html.BeginForm() to remember Querystring params when submitting via GET

I have a form rendered via Html.BeginForm(), it exists as a component in the Master page so that it appears on every page in the application. I have done this using Html.RenderAction() from Mvc Futures assembly. It's a simple search form that updates some items in the same component underneigh the search form itself, and performs a GET so that the search term appears in the querystring.
<div class="sideBarContent">
<h2>Search Products</h2>
<% using (Html.BeginForm(ViewContext.RouteData.Values["action"].ToString(),
ViewContext.RouteData.Values["controller"].ToString(), FormMethod.Get)) { %>
<fieldset>
<legend>Search Products</legend>
<div class="formRow">
<label for="ProductsSearch">Search</label>
<%= Html.TextBox("ProductsSearch") %>
</div>
<input type="submit" value="Search" class="button" />
</fieldset>
<% } %>
<ul>
// Products will eventually be listed here
</ul>
</div>
I need this form to do the following:
1) It should perform a GET to whatever current page it is on appending 'ProductsSearch' as a querystring parameter (eg. example.com/?ProductsSearch=test or example.com/books/fiction?ProductsSearch=test)
2) It should remember any exising querystring parameters that are already in the querystring, maintaining them after you click Search button eg. example.com/myOrders?page=2 after Search click it should go to example.com/myOrders?page=2&ProductsSearch=test)
I can get it to do 1) but can't work out 2).
I relise that normally for a from to GET and appending querystring params it needs to have hidden form fields, so I could write a utility function that automatically adds a bunch of hidden form fields for any querystring values, but I wanted to check that there's wasn't an easier approach, or maybe I'm going about it the wrong way.
Cheers!
You'll need to do the hidden form field method.
Even if you could attach the entire querystring to the end of the URL in the action attribute of the <form> tag, browsers don't pay attention to this when doing GET form submissions.
Your method isn't too difficult; you'd want to do something like this:
public static string QueryStringAsHidden(this HtmlHelper helper)
{
var sb = new StringBuilder();
foreach (var key in HttpContext.Current.Request.QueryString.AllKeys)
{
if (! key.StartsWith("ProductSearch"))
sb.Append(helper.Hidden(key, HttpContext.Current.Request.QueryString[key]));
}
return sb.ToString();
}
I put the .StartsWith() in there because you don't want to be on a search page and submit the search string twice (and now you can prepend paging and other search-specific variables with ProductSearch.
Edit: PS: To get the form to post to the current page, you don't have to explicitly provide action and controller -- you can also send nulls.
Edit2: Why even bother with a helper method? :)
<% HttpContext.Current.Request.QueryString.AllKeys.Where(k => !k.StartsWith("ProductSearch")).ToList().ForEach(k => Response.Write(Html.Hidden(k, HttpContext.Current.Request.QueryString[k]))); %>
James
A direct to call BeginForm() does keep your query string values. Any other overload tends to fail. I love the ease of using BeginForm() from my forms, but needed a way to class all my styled forms a certain way an not lose the query string values in the action.
Here is what I came up with:
public static MvcForm BeginNormalForm<T>(this HtmlHelper<T> htmlHelper)
{
var dictionary = new Dictionary<string, object> {{"class", "normal"}};
var rvd = new RouteValueDictionary();
if (htmlHelper.ViewContext.HttpContext != null && htmlHelper.ViewContext.HttpContext.Request != null)
{
foreach (var key in htmlHelper.ViewContext.HttpContext.Request.QueryString.AllKeys)
{
rvd[key] = htmlHelper.ViewContext.HttpContext.Request.QueryString[key];
}
}
var form = htmlHelper.BeginForm(null, null, rvd, FormMethod.Post, dictionary);
return form;
}
Seems to work well and keeps my class attribute.
Use one of the overloads of BeginForm that takes a routeValues object or dictionary.
Additional properties not in the route will be added as query parameters.

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