How to TryParse for Enum value?

c# enums
Manish Basantani picture Manish Basantani · Jul 4, 2009 · Viewed 105k times · Source

I want to write a function which can validate a given value (passed as a string) against possible values of an enum. In the case of a match, it should return the enum instance; otherwise, it should return a default value.

The function may not internally use try/catch, which excludes using Enum.Parse, which throws an exception when given an invalid argument.

I'd like to use something along the lines of a TryParse function to implement this:

public static TEnum ToEnum<TEnum>(this string strEnumValue, TEnum defaultValue)
{
   object enumValue;
   if (!TryParse (typeof (TEnum), strEnumValue, out enumValue))
   {
       return defaultValue;
   }
   return (TEnum) enumValue;
}

Answer

Thorarin picture Thorarin · Jul 4, 2009

Enum.IsDefined will get things done. It may not be as efficient as a TryParse would probably be, but it will work without exception handling.

public static TEnum ToEnum<TEnum>(this string strEnumValue, TEnum defaultValue)
{
    if (!Enum.IsDefined(typeof(TEnum), strEnumValue))
        return defaultValue;

    return (TEnum)Enum.Parse(typeof(TEnum), strEnumValue);
}

Worth noting: a TryParse method was added in .NET 4.0.

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