I have an enum as below:
public enum MyEnum { One, Two, Three}
And I would like to pare some strings to above enum, for example, below strings are going to be parsed as MyEnum.Two:
"Two", "TWO", "Second", "2"
I know I can maintain a mapping function to do this job. However, I just want to find a better way, for example, override Enum.Parse function, or something like that. I have tried to use IConvertable, but it seems not possible. Any idea?
[AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
public class NameAttribute : Attribute
{
public readonly string[] Names;
public NameAttribute(string name)
{
if (name == null)
{
throw new ArgumentNullException();
}
Names = new[] { name };
}
public NameAttribute(params string[] names)
{
if (names == null || names.Any(x => x == null))
{
throw new ArgumentNullException();
}
Names = names;
}
}
public static class ParseEnum
{
public static TEnum Parse<TEnum>(string value) where TEnum : struct
{
return ParseEnumImpl<TEnum>.Values[value];
}
public static bool TryParse<TEnum>(string value, out TEnum result) where TEnum : struct
{
return ParseEnumImpl<TEnum>.Values.TryGetValue(value, out result);
}
private static class ParseEnumImpl<TEnum> where TEnum : struct
{
public static readonly Dictionary<string, TEnum> Values = new Dictionary<string,TEnum>();
static ParseEnumImpl()
{
var nameAttributes = typeof(TEnum)
.GetFields()
.Select(x => new
{
Value = x,
Names = x.GetCustomAttributes(typeof(NameAttribute), false)
.Cast<NameAttribute>()
});
var degrouped = nameAttributes.SelectMany(
x => x.Names.SelectMany(y => y.Names),
(x, y) => new { Value = x.Value, Name = y });
Values = degrouped.ToDictionary(
x => x.Name,
x => (TEnum)x.Value.GetValue(null));
}
}
}
Then you can (note the double syntax for [Name]
, multiple [Name]
or single [Name]
with multiple names):
public enum TestEnum
{
[Name("1")]
[Name("Foo")]
[Name("F")]
[Name("XF", "YF")]
Foo = 1,
[Name("2")]
[Name("Bar")]
[Name("B")]
[Name("XB", "YB")]
Bar = 2
}
and
TestEnum r1 = ParseEnum.Parse<TestEnum>("XF");
TestEnum r2;
bool r3 = ParseEnum.TryParse<TestEnum>("YB", out r2);
Note the use of an inner class (ParseEnumImpl<TEnum>
) to cache the TEnum
"names".
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