Question

I asked a previous question about mapping an enumerated value on a table using LinqToSql and the answer was to use the O/R Designer to set the type to global::MyNamespace.TMyEnum.

That works OK if your enumeration is based on an integer. But what if your enum is based on a string value? The most obvious application of this is:

public enum TGender {
  Male,
  Female,
  Unknown,
}

where the equivalent values on the database are M, F and U. You can’t type an enumeration as a string, so how can you make the Gender property of your LinqToSql object return a TGender value?

Answer 1

I’d add a getter property to my LINQ to SQL object that looks something like this:

public TGender Gender
{
   switch(this.DbGender)
   {
      case "M":
        return TGender.Male;
   }
}

Or, if you don’t want to use a huge switch statement, you can add an attribute to your enum, that has a string property that represents the string value in the database for that value. Then, use reflection, get the correct enum, and return that.

Here’s a sample of doing it using Reflection and Attributes:

public class EnumAttribute : Attribute
{
    public string DbValue
    {
        get;
        set;
    }
}

public enum TGender
{
    [EnumAttribute(DbValue = "M")]
    Male,
    [EnumAttribute(DbValue = "F")]
    Female,
    [EnumAttribute(DbValue = "U")]
    Unknown
}

    public TGender GetEnumValue(string s)
    {
        foreach (TGender item in Enum.GetValues(typeof(TGender)))
        {
            FieldInfo info = typeof(TGender).GetField(item.ToString());
            var attribs = info.GetCustomAttributes(typeof(EnumAttribute), false);
            if (attribs.Length > 0)
            {
                EnumAttribute a = attribs[0] as EnumAttribute;
                if (s == a.DbValue)
                {
                    return item;
                }
            }
        }

        throw new ArgumentException("Invalid string value.");
    }

To test it out:

var item = GetEnumValue("M");
Console.WriteLine(item);

This results in “Male”.