Why I can't use Enum Parameter in This Function

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1.33/5 (3 votes)

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C#

public static void LoadHemCombo(ComboBox cbo,Enum myEnum)
       {
           cbo.DataSource = Enum.GetValues(typeof(myEnum))
               .Cast<Enum>()
               .Select(value => new
               {
                   (Attribute.GetCustomAttribute(value.GetType().GetField(value.ToString()), typeof(DescriptionAttribute)) as DescriptionAttribute).Description,
                   value
               })
               .OrderBy(item => item.value)
               .ToList();
           cbo.DisplayMember = "Description";
           cbo.ValueMember = "value";
       }

this function works without enum parameter. I found the function at
http://codereview.stackexchange.com/questions/39163/loading-a-combobox-with-an-enum-and-binding-to-it[^]

Posted 13-Mar-15 5:58am

amagitech

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Richard Deeming 13-Mar-15 12:18pm

Maybe if you tried copying the code from the solution, rather than making random changes to it without understanding what it does?

The code in the solution doesn't have an Enum parameter, so why does yours?

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manchanx · Accepted Answer · 2015-03-13T06:18:00

This:

C#

typeof(myEnum)

doesn't work because myEnum is your enum variable, not your enum type.

Instead you have to write the name of your enum-definition there - the equivalent to what is HemEnum in the source you linked:

C#

public enum HemEnum
{
    [Description("none")]
    HemNone = -1,
    [Description("sewn")]
    Hemsew = 0,
    [Description("welded")]
    HemWeld = 1,
    [Description("double folded")]
    Hemdoublefold = 2
}

So, if your enum type is named "Abcdef" you have to write:

C#

public static void LoadHemCombo(ComboBox cbo)
{
    cbo.DataSource = Enum.GetValues(typeof(Abcdef))
    // rest identical

I excluded the myEnum parameter of your method there because I don't know what it is supposed to be good for - it's not needed/used in the method.

edit after comment:

To use this with several different Enum-Types, make it a generic method:

C#

public static void LoadCombo<TEnum>(ComboBox cbo)
       {
           cbo.DataSource = Enum.GetValues(typeof(TEnum))
               .Cast<Enum>()
               .Select(value => new
               {
(Attribute.GetCustomAttribute(value.GetType().GetField(value.ToString()), typeof(DescriptionAttribute)) as DescriptionAttribute).Description,
                   value
               })
               .OrderBy(item => item.value)
               .ToList();
           cbo.DisplayMember = "Description";
           cbo.ValueMember = "value";
       }

Example use:

C#

public enum YourEnumType1
{
  [Description("foo")]
  abc,
  [Description("bar")]
  def,
  [Description("baz")]
  ghi
}

// wherever you want to initialize the combobox that should show YourEnumType1:

LoadCombo<YourEnumType1>(cbo);