How to convert date of varying formats

Question

So I have a string that could be a date of varying formats. I wanted to create a method that tries each one until it is successful, then return the converted date, or throw an error if it matches no formats. I wrote this:

private string ConvertDate(string toConvert)
{
    if (string.IsNullOrEmpty(toConvert)) { return ""; }

    DateTime date;
    bool success = DateTime.TryParseExact(toConvert,
            "MMddyy",
            new CultureInfo("en-US"),
            DateTimeStyles.None,
            out date);

    if (!success)
    {
        success = DateTime.TryParseExact(toConvert,
            "MMddyyyy",
                new CultureInfo("en-US"),
            DateTimeStyles.None,
            out date);
    }
    if (!success)
    {
        success = DateTime.TryParseExact(toConvert,
            "MM/dd/yy",
            new CultureInfo("en-US"),
            DateTimeStyles.None,
            out date);
    }
    if (!success)
    {
        success = DateTime.TryParseExact(toConvert,
            "MM/dd/yyyy",
            new CultureInfo("en-US"),
            DateTimeStyles.None,
            out date);
    }
    if (!success) throw new Exception("Date formats are not recognized");

    return date.ToString();
}

It works, but I feel pretty silly writing all that, I figure there must be an easier way to check a lot of different date formats in 1 pass. Any ideas?

Answer 1

This is at least easier to maintain. Although the function name is misleading. It's should probably be something like StandardizeDateFormat.

private string ConvertDate(string toConvert)
{
    if (string.IsNullOrEmpty(toConvert)) { return ""; }

    string[] dateFormats = new string[]{"MMddyy","MMddyyyy","MM/dd/yy","MM/dd/yyyy"};
    DateTime date;
    bool success = false;
    for(int i = 0;i<dateFormats.Length &&!success;i++)
    {
        success = DateTime.TryParseExact(toConvert,
        dateFormats[i],
            new CultureInfo("en-US"),
            DateTimeStyles.None,
            out date);
    }
    if (!success) throw new Exception("Date formats are not recognized");

    return date.ToString();
}

Edit: Actually, I would probably simplify it even further like so

private string ConvertDate(string toConvert)
{
    if (string.IsNullOrEmpty(toConvert)) { return ""; }

    string[] dateFormats = new string[]{"MMddyy","MMddyyyy","MM/dd/yy","MM/dd/yyyy"};
    DateTime date;
    for(int i = 0;i<dateFormats.Length ;i++)
    {
        if(DateTime.TryParseExact(toConvert, dateFormats[i], new CultureInfo("en-US"), DateTimeStyles.None, out date))
            return date.ToString();
    }
    throw new Exception("Date formats are not recognized");
}

Answer 2

Try something like this. Assuming MM is always first and year is 2000 or later (for yy format)

string date = "10/25/2011";
string[] arr = date.ToArray() 
              .Where(ch => ch > 47 && ch < 58 ) //Filter out all but numbers
              .Select(s => s.ToString()).ToArray(); 

if(arr.Length >5)
{
   string ISOformattedDate = string.Format( arr.Length == 6 ? 
          "{4}{5}-{0}{1}-{2}{3}T00:00:00" : 
          "{4}{5}{6}{7}-{0}{1}-{2}{3}T00:00:00", arr);
   DateTime mydate = Convert.ToDateTime(ISOformattedDate);
}