Check that integer type belongs to enum member

Question

I want to check that some integer type belongs to (an) enumeration member.

For Example,

public enum Enum1
{
    member1 = 4,

    member2 = 5,

    m         


        

Answer 1

Here's a succinct little snippet from an extension method I wrote a few years ago. Combines TryParse with IsDefined to do it all in one swoop and handle values that don't exist in the enum.

if (value != null)
{
    TEnum result;
    if (Enum.TryParse(value.ToString(), true, out result))
    {
        // since an out-of-range int can be cast to TEnum, double-check that result is valid
        if (Enum.IsDefined(typeof(TEnum), result.ToString() ?? string.Empty))
        {
            return result;
        }
    }
}

Here's the extension for integer values

public static TEnum ParseToEnum(this int value, TEnum? defaultValue = null, bool useEnumDefault = false) where TEnum : struct
{
    return ParseToEnumInternal(value, defaultValue, useEnumDefault);
}

And a usage

public enum Test
{
    Value1 = 1,
    Value2 = 3
}
    
var intValue = 1;
var enumParsed = intValue.ParseToEnum(); // converts to Test.Value1
intValue = 2;
enumParsed = intValue.ParseToEnum(); // either throws or converts to supplied default
enumParsed = 3.ParseToEnum(); // converts to Test.Value2

Some people don't like how it dangles off the end of the (potentially nullable) value, but I have an extension that handles null values of nullable types (int?) and I like it myself, so ...

I can post like a Gist of the whole extension method with all the overloads if you're interested.