How do I presist data from the view during EDIT GET to EDIT POST? - asp.net-mvc-3

Question

I have a dilemma that I hope someone can help me with. During the Edit Get stage of loading and updating a page before it is loaded, I store the checkboxes that are checked like this:
foreach (var course in courses.Select((x, i) => new { Data = x, Index = i }))
{
#: <td>
<br /><br /><br />
<input type="checkbox" id="checkbox" name="selectedCourses" value="#course.Data.CourseID"
#(Html.Raw(course.Data.Assigned ? "checked=\"checked\"" : "")) />
</td>
bool theNewString = course.Data.Assigned;
String a = theNewString.ToString();
assignedCourses.Add(a);
}
At the top of the view I defined the list to store the data like this so that I can be sent in the BeginForm:
#{ List<String> assignedCourses = new List<String>(); }
Then I try to send the list to the Edit POST like this:
#using (Html.BeginForm(new { assigned = assignedCourses }))
In my controller signature looks like this:
[HttpPost]
public ActionResult Edit(int id, List<String> assigned)
The list is loaded at the end of the get stage but the data in the list does not go through to Edit POST. My question is how do I get the list that I created at the end of the edit get stage to persist so that I can use it in my post?
Thanks for any ideas.

Answer 1

I'll try make this as simple as possible. So your Course model is something like this...
public class Course
{
public int Id { get; set; }
public string Name { get; set; }
public bool Assigned { get; set; }
}
...and you want to display some saved values on screen to edit. So starting at the controller, I've dummied some data and set one of the Assigned booleans to true so it is checked when the page loads.
public Controller Courses
{
public ActionResult Edit(int id)
{
var courses = new Course[] {
new Course() { Id = 1, Name = "maths", Assigned = true },
new Course() { Id = 2, Name = "english", Assigned = false },
new Course() { Id = 3, Name = "science", Assigned = false }
};
return View(courses);
}
Now, your page should expect a collection of these courses, so at the top of your page define the type that the View is expecting...
cshtml
#model IEnumerable<ExampleProject.Domain.Course>
...which you can then enumerate through in your View and create your checkboxes.
#using (Html.BeginForm("Edit", "Courses", FormMethod.Post))
{
#foreach(var item in Model)
{
<label for="#item.Id">#item.Name</label>
<input type="checkbox" name="courses" id="#item.Id" value="#item.Id" checked="#item.Assigned" />
}
<button type="submit">Save changes</button>
}
This will render the following html:
<label for="1">maths</label>
<input type="checkbox" name="courses" id="1" value="1" checked="checked">
<label for="2">english</label>
<input type="checkbox" name="courses" id="2" value="2">
<label for="3">science</label>
<input type="checkbox" name="courses" id="3" value="3">
Now you can check what you like and submit your form. In true http fashion your controller action will receive the values were checked on the View:
[HttpPost]
public ActionResult Courses(int id, int[] courses)
{
// courses will contain the values of the checkboxes that were checked
return RedirectToAction("Index"); // etc
}
Hopefully this helps. You can be a bit smarter and use the Html helpers for some more complicated binding (eg. Html.CheckBox, Html.CheckBoxFor) but this should get you going and it's clear to see what's going on.