Create a List of objects using enum data C#

Question

So I have an enum:

public enum myEnum
{
    IBM = 1,
    HP = 2,
    Lenovo = 3
}

I have a Brand class

public class Brand
{
    public Brand(string name, int id)
    {
        Name = name;
        Id = id;
    }

    public string Name { get; private set; }
    public int Id { get; private set; }
}

I want to create a List of Brand objects populated with the data from the MyEnum. Something like:

private IEnumerable<Brand> brands = new List<Brand>
{
    new Brand(myEnum.IBM.ToString(), (int) myEnum.IBM),
    new Brand(myEnum.HP.ToString(), (int) myEnum.HP),
    new Brand(myEnum.Lenovo.ToString(), (int) myEnum.Lenovo),
};

I can create two arrays - one with enum names and the other with enum ids and foreach them to create Brand object for every iteration but wonder if there is a better solution.

Finally, I am going with Royi Mindel solution as according to me it is the most appropriate . Many thanks to Daniel Hilgarth for his answer and his help making Royi Mindel suggestion work. I would give credit to both of them for this question if I could.

public static class EnumHelper
{
    public static IEnumerable<ValueName> GetItems<TEnum>() 
        where TEnum : struct, IConvertible, IComparable, IFormattable
    {
        if (!typeof(TEnum).IsEnum)
            throw new ArgumentException("TEnum must be an Enumeration type");

        var res = from e in Enum.GetValues(typeof(TEnum)).Cast<TEnum>()
                  select new ValueName() { Id = Convert.ToInt32(e), Name = e.ToString() };

        return res;
    }
}

public struct ValueName
{
    public int Id { get; set; }
    public string Name { get; set; }
}

Take a look at [`Enum.GetNames()`](http://msdn.microsoft.com/en-us/library/system.enum.getnames.aspx). — CodeCaster, Oct 07 '13 at 08:37
keep only MyEnum in Brand class, and create a property that return enum.ToString() if required — Arsen Mkrtchyan, Oct 07 '13 at 08:37
For concision and re-use I'd just have a constructor taking an instance of the enum, but it's fine as it is really. — stevepkr84, Oct 07 '13 at 08:37
[This might help](http://stackoverflow.com/questions/105372/how-do-i-enumerate-an-enum) — musefan, Oct 07 '13 at 08:38
Do you really need the `enum`? Why can't you just hardcode the values in `brands`? — Ahmed KRAIEM, Oct 07 '13 at 08:39
@MaxMommersteeg: This is C#, not C++. While not illegal, it is certainly not necessary and shouldn't be used. — Daniel Hilgarth, Oct 07 '13 at 08:41
@DanielHilgarth, don't know if it is required for C#, but Microsoft does use it all the time in it's examples: http://msdn.microsoft.com/en-us/library/sbbt4032.aspx — Max, Oct 07 '13 at 08:47
@MaxMommersteeg: IMHO, this is a carry-over from the old C++ days, because the original .NET developers were all C++ developers. In any case, it is not required and has nothing to do with this question. — Daniel Hilgarth, Oct 07 '13 at 08:48
@MaxMommersteeg: BTW: StyleCop does highlight the semicolon as a problem: *"The code contains an extra semicolon. [StyleCop Rule: SA1106]"* — Daniel Hilgarth, Oct 07 '13 at 08:53

score 13 · Answer 1 · answered Oct 07 '13 at 08:37

13

var brands = Enum.GetValues(typeof(myEnum))
                 .Cast<myEnum>()
                 .Select(x => new Brand(x.ToString(), (int)x))
                 .ToArray();

answered Oct 07 '13 at 08:37

Daniel Hilgarth

171,043
40
335
443

4

The downvoter is encouraged to leave a comment, so I can fix what ever you think is incorrect. Hint: I tested this code and it works. – Daniel Hilgarth Oct 07 '13 at 08:49

Royi Mindel · Accepted Answer · 2013-10-07T12:06:47.777

3

I would suggest making a general ValueName class to fit all enums and not make specific classes to fit specific enums

public static class EnumHelper
{
    public static IEnumerable<ValueName> GetItems<TEnum>() 
        where TEnum : struct, IConvertible, IComparable, IFormattable
    {
        if (!typeof(TEnum).IsEnum)
            throw new ArgumentException("TEnum must be an Enumeration type");

        var res = from e in Enum.GetValues(typeof(TEnum)).Cast<TEnum>()
                    select new ValueName() { Value = Convert.ToInt32(e), Name = e.ToString()};

        return res;
    }

}

public struct ValueName
{
    public int Value { get; set; }
    public string Name { get; set; }
}

then you just do :

EnumHelper.GetItems<myEnum>()

edited Oct 07 '13 at 12:06

answered Oct 07 '13 at 08:40

Royi Mindel

1,258
12
35

I like your generic solution. But I need the Value property to be of type int, and I am unable to cast: select new ValueName() { Value = (int)e, Name = e.toString() }. Suggestions ? – Mdb Oct 07 '13 at 09:22
It gives error - Cannot cast expression of type 'System.Enum' to type TEnum. – Mdb Oct 07 '13 at 09:43
No, same error. Thanks anyway. I will go with Daniel Hilgarth way. Really like your approach though. – Mdb Oct 07 '13 at 10:38
2

To make it work, simply replace `Cast` with `Cast` and remove the strange `GetEnumInt` method with a simple `Convert.ToInt32`. Check my answer for reference. – Daniel Hilgarth Oct 07 '13 at 10:43
Updated the answer to the working one, thanks @DanielHilgarth – Royi Mindel Oct 07 '13 at 12:07
@RoyiMindel: That doesn't work. You need to use `Convert.ToInt32` instead of a simple cast. – Daniel Hilgarth Oct 07 '13 at 12:08

score 2 · Answer 3 · edited May 23 '17 at 12:34

Your code was very good, but I was change bit level simplification for your code.

Enum class (Does Not changed):

public enum myEnum
{
    IBM = 1,
    HP = 2,
    Lenovo = 3
}

Brand class(Change parameter length, you can pass one parameter of Enum):

public class Brand
{
    public Brand(Enum Data)
    {
        Name = Data.ToString();
        Id = Convert.ToInt32(Data); 
    }

    public string Name { get; private set; }
    public int Id { get; private set; }
}

And here is change this way:

private IEnumerable<Brand> brands = new List<Brand>
{
    new Brand(myEnum.IBM),
    new Brand(myEnum.HP),
    new Brand(myEnum.Lenovo),
};

And You like see this sample : C# Iterating through an enum? (Indexing a System.Array)

Thank You for your answer, Ramesh! I believe with my way the Brand class interface and usage is more clearer - it accepts name and id and initialize the corresponding properties. — Mdb, Oct 07 '13 at 08:55

Create a List of objects using enum data C#

3 Answers3