Imagine a page which uses checkboxes to keep track of mailing list subscriptions about pets:
cats-list ( )
dogs-list (*)
birds-list ( )
horses-list (*)
I use ASP.NET MVC's Html.Checkbox extension method in a loop (not shown):
<%= Html.Checkbox("subscriptions[" + i +"]", item.subscribed, item.listName) %>
"i" is the iteration variable in the loop. Using this convention allows my controller action to model bind subscriptions[i] to a List<string> which then contains a list of mailing list names to subscribe to.
How can I keep track of what's not checked? For example, if a user unchecks "dogs-list" to unsubscribe from that list, how can I tell? I'll only get "false" back from the hidden form field.
EDIT: The only solution which comes to mind is for the controller action to unsubscribe from all mailing lists, and then resubscribe to lists contained in the List<string> from the checkboxes. That's not ideal though.
You basically answered it yourself with the edit but something a bit more elegant would be better. I.e. Don't delete them all first, just determin which need to be added, which need to be deleted and which need to just remain.
E.g. (air code)
List<string> selectedSubscriptions; //This is passed in from the form using the model binder
List<string> mailingListsToRemove = GetCurrentMailingLists(); //Looks odd but bear with me
List<string> mailingListsToAdd = new List<string>();
//Loop through all the mailing lists they had selected
foreach (string selectedMailingList in selectedSubscriptions)
{
//if the mailing list exists in the list to remove, remove it from that list
//because they obviously don't want it removed
//Remember that this list also contains their current lists.
if (mailingListsToRemove.Contains(selectedMailingList))
{
mailingListsToRemove.Remove(selectedMailingList);
}
else //If it's not in the list to remove then add it
{
mailingListsToAdd.Add(selectedMailingList);
}
}
So at the end of that loop you should have two lists - one containing all the mailing lists that the user wants removed and one containing all the new mailing lists they want to be subscribed to. The mailing lists that they were already subscribed to and still wish to be subscribed to should just be left alone.
HTHs,
Charles
Related
I am just starting learning MVC and I am stuck on this issue. I will appreciate if anyone has come across this before. Thanks
I would like to display the list by station. E.g Police of New-York can only see list of offences in New-York.
enter image description here This is the most recent change but still not working.
I would like to display the list of offences by the USER state.
At the moment I am displaying all the users regardless of their state id.
Here are two options that come to mind. One, you can filter out the offenses by iterating over them and pulling out only the values you need into a new list in C#. Two, you could edit the stored procedure to pass in parameters (such as a State ID or User ID) and then filter out the list of offenses returned from the database using a WHERE clause. Below is some sample code based on your image.
Idea One:
public ActionResult ViewOffenceList(int filterStateID)
{
PageModel model = new PageModel();
DBFile db = new DBFile();
var details = db.Offence.ToList();
List<Offence> filteredList = new List<Offence>();
foreach (var offence in details)
{
if (offence.StateID == filterStateID)
{
filteredList.Add(offence);
}
}
model.OffenceList = filteredList;
return View(model);
}
Idea Two:
CREATE PROCEDURE dbo.fwsp_GetOffenceList
#FilterStateID TINYINT
AS
SELECT *
FROM dbo.offences o
WHERE o.StateID = #FilterStateID
GO
These are just some quick overviews of the two options that come to mind given my experiences. In general, grab the ID of the state you wish to filter on, and use that to filter out which data to actually display. It sounds like you may have a User object which may have an associated State which you could use as the "filterStateID" in my examples.
If you're just starting out I'd suggest finding some tutorials online and walking through them. Here's one directly from Microsoft: https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-mvc-app/start-mvc?tabs=aspnetcore2x
My application needs to do an HTTP post of a table with checkboxes like in the image above. On the controller side I will need to traverse the table and perform certain operations for each row that was checked.
The things that I need to do are:
Identify whether a row is checked
Get the cell values of a checked row
I have a good understanding on how this will be done in Razor in as far as posting the form is concerned. But I am clueless once I am in my controller's action method.
Please help. Thanks.
From what you've show, it appears that all you really need in your action method is a collection of ids to identify which "rows" to modify. I'd use a series of checkboxes with values set to the id of the row they represent. Presumably you have some sort of persistence mechanism in which these rows can be looked up or have them cached server side.
[HttpPost]
public ActionResult Update( List<int> rowIDs ) // where your checkboxes are named rowIDs
{
var messages = DB.Messages.Where( m => rowIDs.Contains( m.ID ) );
foreach (var message in messages)
{
// process the update
}
DB.SaveChanges();
return RedirectToAction( "index" ); // display the updated list
}
Note that it's more likely that you have a model with the collection of ids as well as some other data representing what "update" to perform. Posting collections can be tricky; you might need to play with the name of the input and/or with hidden indexes if you're not getting all the data posted back as expected.
I have a class called "PropertyFeature" which simply contains PropertyFeatureID and Description. It's a proper model created through LINQ to SQL mapped to an SQL Server database table. An example instance/row would be:
PropertyFeatureID: 2
Description: "Swimming Pool"
The number of rows (PropertyFeatures) can of course grow and shrink, and so I want to dynamically render a list of checkboxes so that the user can select any of them.
I can dynamically render the Checkboxes easily enough, with something like:
<%foreach (var Feature in (ViewData["Features"] as IEnumerable<MySolution.Models.PropertyFeature>)) { %>
<%=Html.CheckBox("Features", new { #id = Feature.PropertyFeatureID, #value = Feature.PropertyFeatureID })%><label for="Feature<%=Feature.PropertyFeatureID%>"><%=Feature.Description%></label>
<%}%>
I specify the ID for each checkbox and render the matching label so that the user can intuitively click the label and toggle the checkbox - that works great.
I set the CheckBox's "name" to "Features" so all the checkboxes render with the same name, and the MVC Model Binder piles them into a single collection called "Features" when the form is posted. This works nicely.
Once the form is submitted, I use the checked values and store them, so I need the actual integer values so I know which PropertyFeature is selected, not just a pile of Booleans and field names. So ideally, I want it as an array or a collection that's easy to work with.
I am able to retrieve the selected values from within my Controller method when the button is clicked because I have specified the parameter as int[] Features.
But the problem is that it doesn't maintain state. That is, when I click the submit button and the page reloads (with the form again displayed) I want all of the dynamic checkboxes to retain their checked status (or not). All of the other fields that I've created with Html.DropDownList and Html.TextBox all maintain their states successfully no problems at all on the same page in the same form.
I have spent hours reading all of the other threads and articles on similar issues and there is a lot of talk about using ICollection and IDictionary to bundle things up and include a Boolean value for each item so that it can maintain the checkbox state. But I don't 100% grasp how to use that in the context of my own personal example. I would like to keep the solution really simple and not have to code up pages of new classes just to maintain my checkbox state.
What is the cleanest and proper way to do this?
I got it working after much playing around with the various different approaches.
In the view:
<%string[] PostFeatures = Request.Form.GetValues("Features");%>
<% foreach (var Feature in (ViewData["AllPropertyFeatures"] as
IEnumerable<MySolution.Models.PropertyFeature>))
{ %>
<input type="checkbox" name="Features"
id="Feature<%=Feature.PropertyFeatureID.ToString()%>"
value="<%=Feature.PropertyFeatureID%>"
<%if(PostFeatures!=null)
{
if(PostFeatures.Contains(Feature.PropertyFeatureID.ToString()))
{
Response.Write("checked=\"checked\"");
}
}
%> />
<label for="Feature<%=Feature.PropertyFeatureID%>">
<%=Feature.Description%></label> <%
} %>
In the receiving controller method:
public ActionResult SearchResults(int[] Features)
This method has a number of advantages:
Allows labels to be clicked to toggle the corresponding checkboxes (usability).
Allows the Controller method to receive a super tidy array of ints, which ONLY contains the ints that have been selected - and not a whole other pile of items which were unselected or containing false/null/blank/0 etc.
Retains the checkbox's checked state when the page reloads containing the form, i.e. the user's selection is retained.
No random/stray type=hidden input fields created from the default ASP.Net MVC Html.CheckBox helper - I know it does those for a good reason, but in this instance, I don't require them as I only want to know about which IDs have been selected and for those to be in a single, tidy int[].
No masses of additional server side bloated classes, helpers and other happy mess required to achieve such a simple thing.
I would recommend this approach for anyone wanting the cleanest / bloat-free solution for a dynamic checkbox list where you need the IDs and you just want to get down to business!
The problem is that when you are rendering your list of checkboxes, you aren't setting any of them as selected. You will need to set your int[] Features in ViewData, and then in your foreach loop, check to see if the ID of that Feature is in the array in ViewData.
something like:
<%=Html.CheckBox("Features",
((int[])ViewData["SelectedFeatures"]).Contains(Feature.PropertyFeatureID),
new { #id = Feature.PropertyFeatureID, #value = Feature.PropertyFeatureID })%
although I didn't test it, so it might not be 100%.
I am new to ASP.NET MVC, particularly ajax operations. I have a form with a jquery dialog for adding items to a drop-down list. This posts to the controller action.
If nothing (ie void method) is returned from the Controller Action the page returns having updated the database, but obviously there no chnage to the form. What would be the best practice in updating the drop down list with the added id/value and selecting the item.
I think my options are:
1) Construct and return the html manually that makes up the new <select> tag
[this would be easy enough and work, but seems like I am missing something]
2) Use some kind of "helper" to construct the new html
[This seems to make sense]
3) Only return the id/value and add this to the list and select the item
[This seems like an overkill considering the item needs to be placed in the correct order etc]
4) Use some kind of Partial View
[Does this mean creating additional forms within ascx controls? not sure how this would effect submitting the main form its on? Also unless this is reusable by passing in parameters(not sure how thats done) maybe 2 is the option?]
UPDATE:
Having looked around a bit, it seems that generating html withing the controller is not a good idea. I have seen other posts that render partialviews to strings which I guess is what I need and separates concerns (since the html bits are in the ascx). Any comments on whether that is good practice.
look at the ContentResult you can specify the mime type of what you return (text/html)
You could alternatively make a control that take a IEnumerable of whatever you put in the selectlist, and build it using the view engine. That way you keep the formatting of the html (in this case a list of options) into a view, and not in your code.
<%# Control Language="C#"Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<Article>>"%>
<%foreach (var article in Model){%>
<option><%:article.Title %></option>
<%} %>
I think I would go for that second one
From what I understood, the jQuery dialog contains a form that, when submitted, will post to an action which updates the database with some information. You want to get the newly added database information and update the same form that was used to trigger the database update.
If that is the case, then I think the best clean and logical option is to return JSON serialization of the items to be put in the drop down right after you update the database. Then, using jQuery, you would clear the drop down and append option tags into it.
You can also write a new, seperate action that returns the JSON serialization of the database objects you need. You would have jQuery call another post to this action as a callback to your first ajax post (the one used to update the database).
Here is a quick snippet
public ActionResult UpdateDatabase(string something)
{
/// update the database
IEnumerable<Items> items = getItemsFromDatabase(); // or w/e
var vals = items.Select(x=> new { value = x.ID, text = x.Name }); // something similar
return Json(vals);
}
Personally, I would write a separate function that returns JSON. This ensure separation of concerns, and gives me a function I can use in many different places.
Returning a JsonResult with all the items is the most versatile and least-bandwidth intensive solution as long as you are happy to iterate through the list in jQuery and update your drop-down list.
Using a partial view is nice for HTML that you can .load(...) directly into your select, but less versatile.
I would go with the JsonResult.
In your Controller:
public JsonResult UpdateItem(string sItem)
{
// 1. Insert new item into database if not exist...
// {update code here}
// 2. retrieve items from database:
IEnumerable<Item> Items = GetItems();
// 3. return enumerable list in JSON format:
return new JsonResult{ Data = new {Items = Items, Result = "OK" }};
}
On client-side:
Iterate through Items array and add the items to your list.
i have this code in my membership service class (taken from the asp.net-mvc sample app)
public MembershipUserCollection GetUnapprovedUsers()
{
MembershipUserCollection users = Membership.GetAllUsers();
MembershipUserCollection unapprovedUsers = new MembershipUserCollection();
foreach (MembershipUser u in users)
{
if (!u.IsApproved)
{
unapprovedUsers.Add(u);
}
}
return unapprovedUsers;
}
i now need a view to show this list of information and allow someone to approve them which will go back to the controller and set the IsApproved property to true.
Create a view which will generate a form containing label and checkbox for each member of the collection. You need to be able to get from the id of the checkbox to the user.
In the HTTP.POST Action method, iterate through the submitted fields looking for set checkboxes, when you find one set the corresponding user to approved.
Obviously the form can display arbitrary details for each user.
To use the inbuilt control helpers takes a bit more effort because you don't have a fixed size model to work with. To achieve something similar I:
Used a non-strongly typed view
populated ViewData["ids"] with IEnumerable<IdType> (which the view would loop over)
For each entry populated ViewData["field" + id] for each field I was displaying in the entity
In the view looped over the ids using ViewData["ids"] to call the HTML helpers with the id of the field.
(That was V1, in V2 I used model state so I could use the inbuilt validation error display support, but that doesn't really apply if you just want to select users.)
The POST processing was similar, repopulating the id list from the database and the looking up in the passed FormCollection.