.NET Tip: Converting Strings to Enum Values

Occasionally, I run across the need to see whether a string holds a valid enumeration value. I prefer to not add comparisons to specific string values when I already have an enumeration with all possible valid values. The solution is to try to convert the string into an enumeration value. If the string does not hold a valid enumeration value, an error will be thrown. If the string does hold a valid enumeration value, you will have a variable with the matching enumeration value that you can work with as needed. First, take a look at the enumeration I'll be using:

public enum DaysOfWeek
{
   Sunday    = 1,
   Monday    = 2,
   Tuesday   = 3,
   Wednesday = 4,
   Thursday  = 5,
   Friday    = 6,
   Saturday  = 7
}

It isn't the most interesting enumeration, but it will suffice. Below, I begin with a string holding the value I want to convert. Next, to do the conversion I use the Enum.Parse() method. The Parse() method takes the type of the enumeration you want to convert to as well as the string to convert. If the conversion succeeds, you now can use CurrentDay however you like in your application. If the string cannot be converted to a valid enumeration value, you can catch the error and process it appropriately.

string CurrentDayString = "Sunday";
DaysOfWeek CurrentDay = DaysOfWeek.Monday;
try
{
   CurrentDay = (DaysOfWeek)Enum.Parse(typeof(DaysOfWeek),
                                       CurrentDayString);
}
catch
{
   // Invalid enumeration value
}

switch (CurrentDay)
{
   case DaysOfWeek.Saturday:
   case DaysOfWeek.Sunday:
      // What are you doing working on the weekend
      break;

   default:
      // Get back to work
      break;
}

The version of Enum.Parse() that I showed in this example is case sensitive. So, if my initial string had been "sunday" instead of "Sunday", it would have thrown an error. There is an overload of Enum.Parse() that accepts an additional boolean value that tells it to ignore case when doing the conversion. Your application will dictate which is most appropriate for you to use.

About the Author

Jay Miller is a Software Engineer with Electronic Tracking Systems, a company dedicated to robbery prevention, apprehension, and recovery based in Carrollton, Texas. Jay has been working with .NET since the release of the first beta and is co-author of Learn Microsoft Visual Basic.Net In a Weekend. Jay can be reached via email at jmiller@sm-ets.com.



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