C#

Parsing strings to enums

Simon Reynolds

Simon Reynolds

— 1 min read

Not something that's needed very often but sometimes we can need to get an enum value from a string, perhaps a value returned from an API you have no control over.

In general, parsing a string to an enum can be done using either

(EnumType)Enum.Parse(typeof(EnumType), stringToConvert);

or

(EnumType)Enum.Parse(typeof(EnumType), stringToConvert, ignoreCase);

This can be used to create an extension method allowing any string to be converted to an enum of any specified type.

/// <summary>
/// Parses a string into an enumeration of Type T
/// </summary>
/// <typeparam name="T">The Enumerator Type</typeparam>
/// <param name="s">The string to parse</param>
/// <param name="defaultValue">The default enumerator to use if the string cannot be parsed</param>
/// <returns>A enumeration of Type T</returns>
public static T ToEnum<T>(this string s, T defaultValue)
{
    if (string.IsNullOrEmpty(s))
    {
        return defaultValue;
    }

    try
    {
       return (T)Enum.Parse(typeof(T), s, true);
    }
    catch (ArgumentException ex)
    {
       return defaultValue;
    }
}

As the default value specifies the enum type, it isn't necessary to explicitly identify the enum type we wish to cast to.
An example would be to convert the name of a day to the appropriate DayOfWeek enum

string day = "Wednesday";
var dayOfWeek = day.ToEnum(DayOfWeek.Monday);
// dayOfWeek = DayOfWeek.Wednesday

string day = "wednesday";
var dayOfWeek = day.ToEnum(DayOfWeek.Monday);
// dayOfWeek = DayOfWeek.Wednesday

string invalidDay = "Wednesdayy";
var dayOfWeek = invalidDay.ToEnum(DayOfWeek.Monday);
// dayOfWeek = DayOfWeek.Monday

An advantage of this approach is that we can specify a default enum which will be used in case a parsing fails as in the final example above

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