Creating a dropdownlist from your controller or view model

问题

How would I create a SelectList in my controller and pass it to my view? I need to give the "-- Select --" option a value of 0.

I'm responding to the replies that I got from Jeremey of Fluent Validation.

This is what I currently have. My view model:

[Validator(typeof(CreateCategoryViewModelValidator))]
public class CreateCategoryViewModel
{
    public CreateCategoryViewModel()
    {
        IsActive = true;
    }

    public string Name { get; set; }
    public string Description { get; set; }
    public string MetaKeywords { get; set; }
    public string MetaDescription { get; set; }
    public bool IsActive { get; set; }
    public IList<Category> ParentCategories { get; set; }
    public int ParentCategoryId { get; set; }
}

My controller.

public ActionResult Create()
{
    List<Category> parentCategoriesList = categoryService.GetParentCategories();

    CreateCategoryViewModel createCategoryViewModel = new CreateCategoryViewModel
    {
        ParentCategories = parentCategoriesList
    };

    return View(createCategoryViewModel);
}

This is what I have in my view:

@Html.DropDownListFor(x => x.ParentCategoryId, new SelectList(Model.ParentCategories, "Id", "Name", Model.ParentCategoryId), "-- Select --")

How do I create a dropdown list in the controller or view model and pass it to the view? I need the "-- Select --" option to have a value of 0.

回答1:

In your model, change the IList<Category> to SelectList and then instantiate it like this...

List<ParentCategory> parentCategories = categoryService.GetParentCategories();

parentCategories.Insert(0, new ParentCategory(){ Id = "0", Name = "--Select--"});

ParentCategories = new SelectList(parentCategories, "Id", "Name");

Then in your view you can simply call

@Html.DropDownListFor(m => m.ParentCategoryId, Model.ParentCategories);

回答2:

One way I've seen it done is to create an object to wrap the id and value of the drop down item, like a List<SelectValue>, and pass it in your ViewModel to the view and then use an HTML helper to construct the dropdown.

public class SelectValue
{
    /// <summary>
    /// Id of the dropdown value
    /// </summary>
    public int Id { get; set; }

    /// <summary>
    /// Display string for the Dropdown
    /// </summary>
    public string DropdownValue { get; set; }
}

Here is the view model:

public class TestViewModel
{
    public List<SelectValue> DropDownValues {get; set;}
}

Here is the HTML Helper:

public static SelectList CreateSelectListWithSelectOption(this HtmlHelper helper, List<SelectValue> options, string selectedValue)
{
    var values = (from option in options
                  select new { Id = option.Id.ToString(), Value = option.DropdownValue }).ToList();

    values.Insert(0, new { Id = 0, Value = "--Select--" });

    return new SelectList(values, "Id", "Value", selectedValue);
}

Then in your view you call the helper:

@Html.DropDownList("DropDownListName", Html.CreateSelectListWithSelect(Model.DropDownValues, "--Select--"))

来源：https://stackoverflow.com/questions/6663615/creating-a-dropdownlist-from-your-controller-or-view-model