How to create a DropDownList from a LINQ query in MVC3?

问题

I need to know how I could create a drop down list to represent all the categories in my "Categories" table.

I have already extracted the names and the values of each category I need, using this LINQ query :

var dbcontext = new LNQ2SQLDataContext();
        var Q = from P in dbcontext.Categories
                where P.SUB_CAT == null
                select P;

I can pass this "Q" to my view like this : In Controller :

return View(Q);

And in the View :

@model IEnumerable<MyAppName.Models.Category>

But I have no idea how to use @html.DropDownListFor() to make a darn good drop down list out of the model. :|

PLUS:

I could make a SelectList from the query "Q" like this :

var category_list = new SelectList(Q, "CAT_ID", "CAT_Name");

BUT I don't know how to create a drop down list (without using ViewBag to pass the category_list to the view) from a simple SelectList, either :|

I searched through as many blogs and websites as I could. But they didn't have the solution for my problem. I only got more and more confused!

So can anybody help please ? :/

回答1:

To use DropDownListFor you'll either have to have a model that has a SelectList or data to make a selectlist out of and a property to store the selected value of the dropdown OR use the ViewBag to pass the category_list. So you can go with...

Public Class MyViewModel
{
    Public Integer SelectedCategory { get; set; }
    Public SelectList Categories { get; set; }
}

Public Class ItemsController : Controller
{
    Public ActionResult Index()
    {
        var dbcontext = new LNQ2SQLDataContext();
        var Q = from P in dbcontext.Categories
                where P.SUB_CAT == null
                select P;
        var vm = new MyViewModel();
        vm.Categories = new SelectList(Q, "CategoryID", "Name");
        return View(vm);
    }

    [HttpPost()]
    Public ActionResult Index(MyViewModel vm)
    {
        var theSelectedCategory = vm.SelectedCategory;
    }
}

The view would be...

@model MyViewModel
@Html.DropDownListFor(model => model.SelectedCategory, Model.Categories, "Select Category")

Note: I don't typically code in C# so I can't guarantee the syntax is exactly right.

来源：https://stackoverflow.com/questions/11758747/how-to-create-a-dropdownlist-from-a-linq-query-in-mvc3

标签

asp.net-mvc-3

linq

selectlist

html.dropdownlistfor