How to use MVC Html Helper .DropDownListFor<> w

问题:

In my MVC 3 Razor app, I have a Model with an enum..

Model Example:

public class EmployeeModel
{
 public enum Title
 {
  Accountant = 111,
  Sales = 222,
  Production = 333 
 }

 [Required]
 public string Name {get; set;}

 [Required]
 public Title JobTitle {get; set;}
}

In my View I would like to use the Html helpers to build an Html Form...

View Example:

@model ..Models.EmployeeModel

@using (Html.BeginForm())
{
 @Html.LabelFor(m => m.Name)
 @Html.TextBoxFor(m => m.Name)
 <br>

 @Html.LabelFor(m => m.JobTitle)
 @Html.DropDownListFor(m => m.JobTitle, ??How do I get Title enum values??)
 <br>

 <input type="submit />
}

The output of the DropDownListFor that I trying to achieve would look like this: Note the option values match the initialized values of the enum

<select name="JobTitle">
 <option value="-1">Choose a Job Title</option>
 <option value="111">Accountant</option>
 <option value="222">Sales</option>
 <option value="333">Production</option>
</select>

How do I get the DropDownListFor<> helper to create a select/option element based on the Title enum of the Model?

Also, is it possible to have the DropDownListFor<> helper to add an extra (that is not part of the enum) similar to the "Choose a Job Title" option in the example above?

回答1:

You could possibly get a String[] with the names of the enum values and create a dropdown from that. In your view model, add a property Titles of type SelectListItem and add the enum values and names to that. You can get the names and values through the System.Enum type.

var defaultItem = new SelectListItem();
defaultItem.Value = -1;
defaultItem.Text = "Choose a title";
defaultItem.Selected = true;
model.TitleSelectItems.add(defaultItem);

String[] names = System.Enum.GetNames(typeof(Title));
Int[] values = System.Enum.GetValues(typeof(Title));

for (int i = 0; i<names.Length; i++)
{
    var item = new SelectListItem();
    item.Text = names[i];
    item.Value = values[i];
    model.TitleSelectItems.Add(item);
}

It's kind of ugly, but it'll work.

回答2:

I just stumbled on this StackO question/answer - not only is my question here an exact duplicate, but the answer given by Mike McLaughlin is the best solution I've seen for using DropdownListFor<> with Enums. Specifically, Mike points us to a solution that he found by Morgan Leroi

Morgan's quick solution is:

@Html.DropDownListFor(model => model.State, new SelectList(Enum.GetValues(typeof(MyNamespace.Enums.States))))

But, Morgan has made an Extension that makes the implementation of the DropDownListFor<> with enums even more compact. You can download Morgan's Visual Studio Solution here.

That said, I think we should close this question as it's an exact duplicate.

回答3:

Here is the solution

public enum Months
{
January=1,
February=2,
March=3,
April =4,
May=5,
June=6
}

public ActionResult Index()
{

ViewBag.Months = (from Months m in Enum.GetValues(typeof(Months))
                select new SelectListItem { Text = m.ToString(), Value = Convert.ToUInt16(m).ToString() });

return View();  
}

Add ViewBag name in DropDownList :

<%=Html.DropDownList("Months") %>

回答4:

Here's a way using Html Helpers:

Model

public class Person
{
    public string Name { get; set; }
    public JobTitle Job { get; set; }
    public enum JobTitle
    {
        Accountant = 111,
        Sales = 222,
        Production = 333
    }
}

View

@model MvcApplication1.Models.Person

@{
    ViewBag.Title = "Index";
}

@using (Html.BeginForm())
{
    @Html.TextBoxFor(n => n.Name)
    @Html.DropDownListFor(c => c.Job, new[]{
        new SelectListItem() {Text = MvcApplication1.Models.Person.JobTitle.Accountant.ToString(), 
            Value=((int)MvcApplication1.Models.Person.JobTitle.Accountant).ToString()}
        ,new SelectListItem() {Text = MvcApplication1.Models.Person.JobTitle.Production.ToString(), 
            Value=((int)MvcApplication1.Models.Person.JobTitle.Production).ToString()}
        ,new SelectListItem() {Text = MvcApplication1.Models.Person.JobTitle.Sales.ToString(),
            Value=((int)MvcApplication1.Models.Person.JobTitle.Sales).ToString()}}
            , "Choose a Job Title")                               
}

HTML Output

<!DOCTYPE html>
<html>
<head>
    <title>Index</title>
</head>
<body>
<form action="/" method="post">
<input id="Name" name="Name" type="text" value="" />
<select id="Job" name="Job">
<option value="">Choose a Job Title</option>
<option value="111">Accountant</option>
<option value="333">Production</option>
<option value="222">Sales</option>
</select>
</form>
</body>
</html>

回答5:

An encapsulated HTML Helper Extension is available here :

http://www.spicelogic.com/Journal/ASP-NET-MVC-DropDownListFor-Html-Helper-Enum-5

the source code snapshot:

You can download the full source code of the project from the link.

回答6:

I solved it with this extension:

public static SelectList ToSelectListWithDefault<TEnum>(this TEnum enumObj, string defValue, string defText) where TEnum : IConvertible
{
    var values = new List<SelectListItem>();
    var defItem = new SelectListItem() { Value = defValue, Text = defText };
    values.Add(defItem);
    foreach (TEnum e in Enum.GetValues(typeof(TEnum)))
    {
        values.Add(new SelectListItem() { Value = e.ToInt16(null).ToString(), Text = e.ToString() });
    }

    return new SelectList(values, "Value", "Text", defItem);
}   

(I found the extension on SO, but without the default value)