Context

When you’re working with a UI or plain text data integration, conversions are often an issue. In this case I would like to talk about DateTime objects.

Recently, there was an issue in one of the other teams. They had a WinForms UI where they wanted to display a DateTime property in two different textboxes, one for the date and another for the time. They had their reasons for not using a DateTimePicker control or any other method. That wasn’t really the problem. One of the business users discovered an error when trying to save changes. The development team figured out what went wrong, apparently it was a “Culture” thing.

The business user’s computer was using Windows XP and its regional settings were set to English – United States. When the application tried to parse the textboxes and store the value back in the property, the month and day were swapped. In Europe we usually use “dd/MM/yyyy”, in the US they use “MM/dd/yyyy”.

Normally this should not pose a problem, the date was successfully loaded, so why wouldn’t it convert back as expected. Well, one of the main reasons is VB.NET. VB.NET has a feature called CDate, which can convert a string to a Date object. In C#, you only have a DateTime object. What happened? The CDate takes the regional settings and when you enter 16/10/2010, it will crash, because there is no 16th month.

Enter Mike

I overheard an intense discussion going on and decided to see if I could be of use. Call it interfering if you want; I see it as helping colleagues ;) . They explained the situation of the custom controls (the two textboxes) and the error. One of them was telling they needed to use DateTimePicker controls, another wanted to change regional settings in the database and application (I missed the point of that one), and so.

After a bit of evaluating, I noticed they were only complicating the solution/problem. I told them they only needed to parse the string into a DateTime object with specific format, and then assign the DateTime to the Date object. So instead of doing a lot of changes, add a single line of code…

I created a helper/utility class on the fly, so they could end their discussion and get back to work (and stop bothering the rest of us :) ).

DateTimeParser

using System;
using System.Globalization;

namespace MyNamespace
{
    public static class DateTimeParser
    {
        public static DateTime ParseDateTime(string value, string inputFormat)
        {
            return ParseDateTime(value, inputFormat, CultureInfo.InvariantCulture);
        }

        public static DateTime ParseDateTime(string value, string inputFormat, CultureInfo provider)
        {
            if (string.IsNullOrEmpty(value))
                throw new ArgumentNullException("value");

            try
            {
                return DateTime.ParseExact(value, inputFormat, provider);
            }
            catch (Exception ex)
            {
                throw new Exception("Could not parse date: " + value, ex);
            }
        }
    }

	public class DateTimeParserDemo
	{
		public DateTime Test()
		{
			string myDate = "31/12/2010 23:59:59";
			return DateTimeParser.ParseDateTime(myDate, "dd/MM/yyyy HH:mm:ss");
		}
	}
}

 

VB.NET code

If you prefer the code in VB.NET head to the website of DeveloperFusion.com, they have an excellent C# to VB.NET converter.