In asp.net mvc3 how to keep dropdown list selected item after postback.
Do something Like this :
[HttpPost]
public ActionResult Create(FormCollection collection)
{ if (TryUpdateModel(yourmodel))
{ //your logic
return RedirectToAction("Index");
}
int selectedvalue = Convert.ToInt32(collection["selectedValue"]);
ViewData["dropdownlist"] = new SelectList(getAllEvents.ToList(), "EventID", "Name", selectedvalue);// your dropdownlist
return View();
}
And in the View:
<%: Html.DropDownListFor(model => model.ProductID, (SelectList)ViewData["dropdownlist"])%>
Even easier, you can include the name(s) of your dropdowns in your ActionResult input parameters. Your dropdowns should be in form tags. When the ActionResult is posted to, ASP.Net will iterate through querystrings, form values and cookies. As long as you include your dropdown names, the selected values will be preserved.
Here I have a form with 3 dropdowns that posts to an ActionResult. The dropdown names are (non-case sensitive): ReportName, Year, and Month.
//MAKE SURE TO ACCEPT THE VALUES FOR REPORTNAME, YEAR, AND MONTH SO THAT THEY PERSIST IN THE DROPDOWNS EVEN AFTER POST!!!!
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult ReportSelection(string reportName, string year, string month)
{
PopulateFilterDrowdowns();
return View("NameOfMyView");
}
MVC does not use ViewState, which means you will need to manage the value persistence yourself. Typically this is done through your model. So, given that you have a view model, e.g.:
public class MyViewModel { }
And your controller:
public class MyController : Controller
{
public ActionResult Something()
{
return View(new MyViewModel());
}
public ActionResult Something(MyViewModel model)
{
if (!ModelState.IsValid)
return View(model);
return RedirectToAction("Index");
}
}
Now, when you pass the model back to the view with data (probably incorrect - failed validation), when you use your DropDownListFor method, just pass in the value:
#Model.DropDownListFor(m => m.Whatever, new SelectList(...))
... etc.
MVC's model binding will take care of the reading of the data into your model, you just need to ensure you pass that back to the view to show the same value again.
Assuming the selected item is part of the post, the controller now knows what it is. Simply have an entry in the ViewData dictionary indicating which item should be selected (null on get or if nothing was selected). In the view, check the value and if it's not null, select the appropriate option.
Use HttpRequestBase object.
In the view, this should work:
#Html.DropDownList("mydropdown", ViewBag.Itens as IEnumerable<SelectListItem>, new { value = Request["mydropdown"] })
If you are building the drop down list data source in the controller Action Method you can send the selected value to it
Controller:
public ActionResult Index( int serviceid=0)
{
// build the drop down list data source
List<Service> services = db.Service.ToList();
services.Insert(0, new Service() { ServiceID = 0, ServiceName = "All" });
// serviceid is the selected value you want to maintain
ViewBag.ServicesList = new SelectList(services, "ServiceID", "ServiceName",serviceid);
if (serviceid == 0)
{
//do something
}
else
{
// do another thing
}
return View();
}
View:
//ServiceList is coming from ViewBag
#Html.DropDownList("ServicesList", null, htmlAttributes: new { #class = "form-control" })
Related
I'm trying to figure out if what I'm doing is flawed or acceptable. Specifically, I'm questioning the NULL value I'm getting back in the POST to Controller in 'Timeframes' property. The 'Timeframe' (singular) property DOES contain the value so all is good. However, is this just how model binding works and the property (Timeframes) that is used to populate the DDL comes back as null? Is this best practice and what I'm doing is fine? Is this a concern of sending values around that are not needed...performance concern?
Timeframe = used to return value back to Controller on Post
Timeframes = used to populate DDL values
Drop Down List Box on View:
#Html.DropDownListFor(m => m.Timeframe, Model.Timeframes)
Model:
public class ABCModel
{
public List<SelectListItem> Timeframes { get; set; }
public string Timeframe { get; set; }
}
Controller:
[HttpPost]
public void TestControllerMethod(ABCModel model)
{
//this value is null.
var timeFrames = model.Timeframes;
//this value is populated correctly
var timeFrame = model.Timeframe;
}
A form only posts back the name/value pairs of its successful controls. You have created a form control for property Timeframe, so you get the value of the selected option in the POST method.
You have not (and should not), created form controls for each property of each SelectListItem in your Timeframes property, so nothing relating to it is send in the request when the form is submitted, hence the value of Timeframes is null.
If you need to return the view because ModelState is invalid, then you need to re-populate the TimeFrames property as you did in the GET method (otherwise your DropDownListFor() will throw an exception). A typical implementation migh look like
public ActionResult Create()
{
ABCModel model = new ABCModel();
ConfigureViewModel(model);
return View(model);
}
[HttpPost]
public ActionResult Create(ABCModel model)
{
if (!modelState.IsValid)
{
ConfigureViewModel(model);
return View(model);
}
// Save and redirect
}
private void ConfigureViewModel(ABCModel model)
{
model.TimeFrames = ....; // your code to populate the SelectList
}
Ok so I have an Html.DropDownList and I want to be able to execute a controller method ActionResult output(string test) and send a parameter to it. I have something like this already but I get an Uncaught TypeError: Cannot set property 'action' of null message:
#Html.DropDownList(
"revisions", ViewData["revisions"] as SelectList,
new
{
onchange = "this.form.action = '/Shops/output('test')'; this.form.submit();"
})
How do I go about fixing my code?
If your Action method's parameter name is id,
public ActionResult output(string id)
{
//do something
}
then you may use your form action url like this.(The default routing will take care of rest)
/Shops/output/somestringhere.
If you have a different name, use that as the query string
public ActionResult output(string name)
{
//do something
}
Now use your form action url like
/Shops/output?name=somestringhere
Another suggestion about your code is to avoid Viewdata for rendering the dropdown. Try to use strongly typed view model and it's properties for transfering data to your view. Also try to move your javascript from your view and make it unobutrusive. So that your view stays as clean markup only.
Assuming you want to show a Revision dropdown in a document create view, Add a property to your viewmodel to have the dropdown items.
public class DocumentCreateViewModel
{
//Other properties also here
public List<SelectListItem> Revisions{ set;get;}
public int SelectedRevision { set;get;}
public DocumentCreateViewModel()
{
Revisions=new List<SelectListItem>();
}
}
and in your GET action, fill the dropdown content to the Revisions property.
public ActionResult Create()
{
var vm=new DocumentCreateViewModel();
vm.Revisions=GetRevisionItemsFromSomeWhere();
return View(vm);
}
And in your strongly typed view,
#model DocumentCreateViewModel
#using(Html.Beginform())
{
#Html.DropDownListFor(x => x.SelectedRevision,
new SelectList(Model.Revisions,"Value","Text"), "Select..")
<input type="submit" />
}
Now to handle the form submit on change event of dropdown, add this script.
$(function(){
$("#SelectedRevision").change(function(){
var _this=$(this);
var selectedRevision=_this.val();
$("form#YourFormIDHere")
.attr("action","./Shops/output/"+selectedRevision).submit();
});
});
Instead of hardcoding the url to shops/output, you may use the razor helper method(#Url.Action) to get the proper path.
#Html.DropDownList(
"revisions", ViewData["revisions"] as SelectList,
new
{
onchange = "submitForm();"
})
and your Javacript goes here
function submitForm()
{
var form = document.forms[0];
form = '/Shops/output?test=test';
form.submit();
}
I am a new to ASP.NET MVC, I am developing an application. I want to bind the data in the drop down list in create view.
How to bind the data in the drop down? I have go through many question and answers here...
I have seen usually everyone suggested to use List<SelectListItem> what is its purpose?
Do I need to use ViewModel while binding the data to drop down list?
Can I get simple example where data get bind in the dropdown using viewbag?
I have created a list in controller
List<string> items = new List<string>();
and I want to pass this list to view using viewbag and simply want to bind to drop down list.
How to do this ?
I'd suggest using a ViewModel as it makes interaction with user input so much easier. Here's an example of how you might bind data from your ViewModel to a drop down in your View. First, the ViewModel:
public class CrowdViewModel
{
public string SelectedPerson { get; set;}
public IEnumerable<SelectListItem> People { get; set; }
}
So yes, you're right - use a collection of SelectListItems. I'm guessing in your case, the SelectListItem's Value and Text property will be the same. You could turn your List into IEnumerable like this:
[HttpGet]
public ActionResult Home()
{
// get your list of strings somehow
// ...
var viewModel = new CrowdViewModel
{
People = items.Select(x => new SelectListItem { Text = x, Value = x })
}
return View(viewModel);
}
Now you need to bind that ViewModel's property to the DropDown on your view. If you're using the Razor ViewEngine, the code will look something like this:
#model MyApp.ViewModels.CrowdViewModel
#using (Html.BeginForm())
{
#Html.DropDownListFor(model => model.SelectedPerson, Model.People)
}
Now when you post that form, MVC will bind the selected value to the ViewModel's SelectedPerson property!
[HttpPost]
public ActionResult Home(CrowdViewModel viewModel)
{
// viewModel.SelectedPerson == whatever the user selected
// ...
}
Easy as that!
Update:
If you really want to use the ViewBag (don't do it), you can pass your list through from your Controller action like so:
[HttpGet]
public ActionResult Home()
{
ViewBag.People = new List<string> { "Bob", "Harry", "John" };
return View();
}
And then create a SelectList on your View:
#Html.DropDownList("SelectedPerson", new SelectList(ViewBag.People, Model))
I using MVC-Viewmodel in my project, my problem is that even if i CTRL-click two values in my listbox It only grabs one value. I want users to be able to select two values but I dont know why it doesnt happen any tips is appreciated!
Here is my GET n POST action inside my controller:
public ActionResult Create()
{
CreateViewModel model = new CreateViewModel();
List<CoreValue> corevalues = Arep.getallC();
model.CoreValuess = new MultiSelectList(corevalues, "CID", "Cname");
return View(model);
}
[HttpPost]
public ActionResult Create(CreateViewModel model)
{
if (ModelState.IsValid)
{
Question q = new Question();
var CoreValueID = int.Parse(model.Cname);
var getallC = Arep.getbycid(CoreValueID);
q.CoreValue.Add(getallC);
q.QuestionText = model.QuestionText;
Arep.addquestion(q);
Arep.save();
return RedirectToAction("Index");
}
return View(model);
This is inside my CreateViewModel:
public MultiSelectList CoreValues { get; set; }
And this is inside my View:
#Html.ListBoxFor(model => model.Cname,Model.Corevaluess)
What seem to be the problem?
Thanks in Advance!
Best Regards
Spelling errors aside, I believe the following is why this is failing:
In your ListBoxFor method, you are using model.Cname. By this, I believe you mean "choose the cName of selected CoreValues". However (and I'm guessing because I can't see your model), the Cname property on the CreateViewModel is of type string. Because of this, you are only ever going to have one value at a time. You need a property that is of type IEnumerable in order to hold multiple selections.
Update your model to the following:
public class CreateViewModel
{
public IEnumerable<string> SelectedValues { get; set; }
public IEnumerable<CoreValue> CoreValues { get; set; }
}
SelectedValues will be used to contain the selected values on the post. We can also add items to it to signify what should be automatically selected when the view is created.
In your controller do the following:
public ActionResult Create()
{
CreateViewModel model = new CreateViewModel();
model.CoreValues = Arep.getallC();
return View(model);
}
Lastly, update the view:
#Html.ListBoxFor(m => m.SelectedValues, new MultiSelectList(Model.CoreValues, "CID", "Cname"))
Now, whenever you post, you should be able to see the values that a user selected.
EDIT: I'm not completely sure what some of your methods do so I'm taking a guess.
The POST method for Create:
[HttpPost]
public ActionResult Create(CreateViewModel model)
{
if (ModelState.IsValid)
{
foreach(var CoreValueID in model.SelectedValues)
{
Question q = new Question();
var getallC = Arep.getbycid(CoreValueID);
q.CoreValue.Add(getallC);
q.QuestionText = model.QuestionText;
Arep.addquestion(q);
}
Arep.save();
return RedirectToAction("Index");
}
return View(model);
}
you would need to pass selectedvalues as below
List<CoreValue> selectedvalues = Null;
model.CoreValuess = new MultiSelectList(corevalues, "CID", "Cname",selectedvalues);
return View(model);
Refer MSDN link and this helpful Article
As stated above, the ASP.Net Mvc wants to have a list of string, but the same thing can be achieved by using the classic ASP style
Request.Form["CoreValues"]
this will provide as comma separated values.
I have a details page which lets me edit the information associated with a particular item.
public ActionResult Details(int id)
{
Call call = db.Calls.Find(id);
return View(new CallFormViewModel(call));
}
I use a view model --
public class CallFormViewModel
{
public Call Call { get; private set; }
public CallFormViewModel()
{
Call = new Call();
}
public CallFormViewModel(Call call)
{
Call = call;
}
}
When I submit, I want to only allow certain properties of the 'call' object to be updated. My Post handling method looks like this -
[HttpPost]
public ActionResult Details(CallFormViewModel callForm)
{
(some code removed for clarity)
UpdateModel(callForm.Call ,new string[] {
"Contact",
"Summary",
"Description",
}
}
The problem is that callForm has already been updated with all of the input from the form submit before I even call UpdateModel.
How can I change this and use UpdateModel to selectively update fields?
Thanks
Edit:
I think i've been looking at this the wrong way. What I should be doing is this:
[HttpPost]
public ActionResult Details(int id, CallFormViewModel callForm)
{
var call = db.Calls.Find(id);
(some code removed for clarity)
UpdateModel(call, "Call", new string[] {
"Contact",
"Summary",
"Description",
}
}
This way it's taking the incomplete data [and only the fields i want] and applying it to the actual model. I had been confusing the callForm.Call with the actual model object, when infact it's only a representation of it.
Have to wait till I get to work to test this theory.
When you write your ViewModel in the Action parameters, The Model Binder Bind the ViewModel properties to the "incoming" data. This should work:
[HttpPost]
public ActionResult Details()
{
CallFormViewModel callForm = new CallFormViewModel();
UpdateModel(callForm.Call ,new string[] {
"Contact",
"Summary",
"Description",
}
}
Update:
The Bind attribute option:
[Bind(Include = "Contact,Summary,Description")]
public class CallFormViewModel
{
// As before...
}
You don't need to call UpdateModel because you will get an updated model passed as the parameter to your method. If you'd prefer to use UpdateModel, you should remove the parameter from the action method.
To then update just the fields you are interested in, you should either:
Have the method take a different view model that only includes the fields that should be updated.
Change the form so that only the fields you want updated are in text boxes (or other updatable controls) created by the HTML.TextBoxFor() methods.