C# MVC: DropDownListFor bind a enum to a integer model-field

Question

How can I bind an enum to a model-field of the type integer?

I tried some extension methods, but they didnt do a good job, cause all method required the model field to be the given enum-type...

Here is my source (Model and Enum):

Model:

public class Einheit
{
    public Einheit()
    {
        Id = Guid.NewGuid();
    }

    public Guid Id { get; set; }
    public short TypeOfSomething { get; set; }
    public long Verwendungszweck { get; set; }
}

Enum:

public enum Einheitsart
{
    Type1 = 0,
    Type2 = 1,
    Type3 = 2,
    Type4 = 3,
    Type5 = 4,
    Type6 = 5
}

I want to have the Values going from 0-6 (To be able to save the Integer in my Model), but the DropDownList should show the Text "Type1" to "Type6"...

The problem I have is converting the enum to a working SelectList.

Thank you!

Answer 1

Try the following helper I created.

Full details can be seen on my blog:

http://www.ninjanye.co.uk/2012/01/creating-dropdown-list-from-enum-in.html

http://jnye.co/Posts/4/creating-a-dropdown-list-from-an-enum-in-mvc-and-c%23

public static class EnumHelper  
{  
    //Creates a SelectList for a nullable enum value  
    public static SelectList SelectListFor<T>(T? selected)  
        where T : struct  
    {  
        return selected == null ? SelectListFor<T>()  
                                : SelectListFor(selected.Value);  
    }  

    //Creates a SelectList for an enum type  
    public static SelectList SelectListFor<T>() where T : struct  
    {  
        Type t = typeof (T);  
        if (t.IsEnum)  
        {  
            var values = Enum.GetValues(typeof(T)).Cast<enum>()  
                             .Select(e => new { Id = Convert.ToInt32(e), Name = e.GetDescription() });  

            return new SelectList(values, "Id", "Name");  
        }  
        return null;  
    }  

    //Creates a SelectList for an enum value  
    public static SelectList SelectListFor<T>(T selected) where T : struct   
    {  
        Type t = typeof(T);  
        if (t.IsEnum)  
        {  
            var values = Enum.GetValues(t).Cast<Enum>()  
                             .Select(e => new { Id = Convert.ToInt32(e), Name = e.GetDescription() });  

            return new SelectList(values, "Id", "Name", Convert.ToInt32(selected));  
        }  
        return null;  
    }   

    // Get the value of the description attribute if the   
    // enum has one, otherwise use the value.  
    public static string GetDescription<TEnum>(this TEnum value)  
    {  
        FieldInfo fi = value.GetType().GetField(value.ToString());  

        if (fi != null)  
        {  
            DescriptionAttribute[] attributes =  
             (DescriptionAttribute[])fi.GetCustomAttributes(  
    typeof(DescriptionAttribute),  
    false);  

            if (attributes.Length > 0)  
            {  
                 return attributes[0].Description;  
            }  
        }  

        return value.ToString();  
    }  
}  

To use it simply use the following code:

//If you don't have an enum value use the type  
ViewBag.DropDownList = EnumHelper.SelectListFor<MyEnum>();  

//If you do have an enum value use the value (the value will be marked as selected)  
ViewBag.DropDownList = EnumHelper.SelectListFor(myEnumValue); 

Note: by adding a description attribute to your enum, it will use that as the display text for the drop down:

public enum Einheitsart
{
    Type1 = 0,
    [Description("2nd Type")]
    Type2 = 1,
    Type3 = 2,
    Type4 = 3,
    Type5 = 4,
    Type6 = 5
}

Answer 2

You can enumerate over all enum values and create SelectListItems for each of them. This should work:

var selectList = new List<SelectListItem>();
foreach(Einheitsart art in Enum.GetValues(typeof(Einheitsart)))
{
    selectList.Add(new SelectListItem() { Value = (int)art, Text = art.ToString() })
}