Can I cast from a generic type to an enum in C#?

I'm writing an utility function that gets a integer from the database and returns a typed enum to the application.

开发者_运维百科Here is what I tried to do (note I pass in a data reader and column name instead of the int in my real function):

public static T GetEnum<T>(int enumAsInt)
{
    Type enumType = typeof(T);

    Enum value = (Enum)Enum.ToObject(enumType, enumAsInt);
    if (Enum.IsDefined(enumType, value) == false)
    {
        throw new NotSupportedException("Unable to convert value from database to the type: " + enumType.ToString());
    }

    return (T)value;
}

But it won't let me cast (T)value saying:

Cannot convert type 'System.Enum' to 'T'.

Also I've read quite a bit of mixed reviews about using Enum.IsDefined. Performance wise it sounds very poor. How else can I guarantee a valid value?

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Like this:

return (T)(object)value;

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Change this:

Enum value = (Enum)Enum.ToObject(enumType, enumAsInt);

to this:

T value = (T)Enum.ToObject(enumType, enumAsInt);

and remove the cast :)

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For information, using the generic constraint Enum is available from C# 7.3 and greater.