What is the best way to strictly parse a string for an enumeration?

Question

Let's say I have an enumeration:

public enum MyEnum
{
    OptionOne = 0,
    OptionTwo = 2,
    OptionThree = 4
}

As said in How do I convert a string to an enumeration question in C #? I am parsing an enumeration from a string using a method Enum.Parse:

public class Enumer
{
    public static MyEnum? ParseEnum(string input)
    {
        try
        {
            return (MyEnum) Enum.Parse(typeof (MyEnum), input);
        }
        catch (ArgumentException)
        {
            return null;
        }
    }

}

Unfortunately, it does not work as expected with integers represented as strings.
I do not expect Parse.Enum () to convert an int from a string, but it actually does.
A simple test:

[TestClass]
public class Tester
{
    [TestMethod]
    public void TestEnum()
    {
        Assert.AreEqual(MyEnum.OptionTwo, Enumer.ParseEnum("OptionTwo"));
        Assert.IsNull(Enumer.ParseEnum("WrongString"));
        Assert.IsNull(Enumer.ParseEnum("2")); // returns 2 instead of null
        Assert.IsNull(Enumer.ParseEnum("12345")); // returns 12345 instead of null
    }
}

Only two out of four checks can be completed.
Enumer.ParseEnum("2")returns MyEnum.OptionTwoinstead null.
Also Enumer.ParseEnum("12345")returns 12345, regardless of scope.

What is the best way to analyze:

• "MyEnum.OptionOne", "MyEnum.OptionTwo", "MyEnum.OptionThree" .
• "MyEnum.OptionOne", "MyEnum.OptionTwo", "MyEnum.OptionThree" 0, 2 4 MyEnum.OptionOne, MyEnum.OptionTwo, MyEnum.OptionThree ?

#? - ​​ , .

Answer 1

, Enum.GetValues(Type enumType).

public static MyEnum? ParseEnum(string input)
{
    return (MyEnum?) Enum.GetValues(typeof(MyEnum)).OfType<object>()
                         .FirstOrDefault(v => v.ToString() == input);
}

, .

public static MyEnum? ParseEnum(string input)
{
    int value;
    var isInt = int.TryParse(input, out value);
    return (MyEnum?) Enum.GetValues(typeof(MyEnum)).OfType<object>()
                         .FirstOrDefault(v => v.ToString() == input
                                           || (isInt & (int)v == value));
}

100% , ,

public static T? ParseEnum<T>(string input)
    where T : struct 
{
    int value;
    var isInt = int.TryParse(input, out value);
    return (T?)Enum.GetValues(typeof(T)).OfType<object>()
                   .FirstOrDefault(v => v.ToString() == typeof(T).Name + input
                                    || (isInt & (int)v == value));
}