Determine if a String is a valid date before parsing

Question

I have this situation where I am reading about 130K records containing dates stored as String fields. Some records contain blanks (nulls), some contain strings like this: \'

Answer 1

You can take advantage of regular expressions to determine which format the string is in, and whether it matches any valid format. Something like this (not tested):

(Oops, I wrote this in C# before checking to see what language you were using.)

Regex test = new Regex(@"^(?:(?\d{2}-[a-zA-Z]{3}-\d{2})|(?\d{2}/\d{2}/\d{3}))$", RegexOption.Compiled);
Match match = test.Match(yourString);
if (match.Success)
{
    if (!string.IsNullOrEmpty(match.Groups["formatA"]))
    {
        // Use format A.
    }
    else if (!string.IsNullOrEmpty(match.Groups["formatB"]))
    {
        // Use format B.
    }
    ...
}