Cannot convert type 'TEnum' to 'int'

Question

I'm trying to convert an enum to a List as mentioned in this example e.g.

Enum.GetValues(typeof(MyEnum)).Cast<MyEnum>().Select(v => new SelectListItem {
    Text = v.ToString(),
    Value = ((int)v).ToString()
}).ToList();

This work but I want to amend it to work with a generic enum

public static List<SelectListItem> GetEnumList<TEnum>(TEnum value)
{

        return Enum.GetValues(typeof(TEnum)).Cast<TEnum>().Select(v => new SelectListItem
        {
            Text = v.ToString(),
            Value = ((int)v).ToString()
        }).ToList();
 }

However the above code doesn't compile and gives

Cannot convert type 'TEnum' to 'int'

for the line

  Value = ((int)v).ToString()

1. How do I fix this above code.

2. Why is it giving a compile error with generic enum and not with a normal enum

---

Edit: I have tried the suggestions in the thread but I get a further error:

Here is my full code:

public static IHtmlContent EnumDropDownListFor<TModel, TResult,TEnum>(
    this IHtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TResult>> expression,
    TEnum enumValue,
    string optionLabel) 
{
    return htmlHelper.DropDownListFor(expression, (IEnumerable<SelectListItem>)GetEnumList(enumValue), optionLabel);
}

public static List<SelectListItem> GetEnumList<TEnum>(TEnum value) 
{
    return Enum.GetValues(typeof(TEnum)).Cast<TEnum>().Select(v => new SelectListItem
    {
        Text = v.ToString(),
        Value = Convert.ToInt32(v).ToString()
    }).ToList();

}

but I get a runtime error

ArgumentException: Type provided must be an Enum.

Parameter name: enumType

on the line

return Enum.GetValues(typeof(TEnum)).Cast<TEnum>().Select(v => new SelectListItem
    {
        Text = v.ToString(),
        Value = Convert.ToInt32(v).ToString()
    }).ToList();

What do I need to fix in the code to not get the runtime error.

Answer 1

You've told the compiler nothing about TEnum. As far as its concerned, it could be a string, a DateTime, a BankAccount, a Bullet or anything.

To get this to work, you can use Enum.Parse and Convert.ToInt32

UPD: Let me just format the code from comment and fix compilation errors for SO-copy-pasters :D

public static int GetEnumIntValue<T>(T value)
    where T : struct
{
    Type genericType = typeof(T);
    Debug.Assert(genericType.IsEnum);
    Enum enumValue = Enum.Parse(genericType, value.ToString()) as Enum;
    return Convert.ToInt32(enumValue);
}