How to Validate a DateTime in C#?

DateTime.TryParse

This I believe is faster and it means you dont have to use ugly try/catches :)

e.g

DateTime temp;
if(DateTime.TryParse(startDateTextBox.Text, out temp))
{
  // Yay :)
}
else
{
  // Aww.. :(
}

Don't use exceptions for flow control. Use DateTime.TryParse and DateTime.TryParseExact. Personally I prefer TryParseExact with a specific format, but I guess there are times when TryParse is better. Example use based on your original code:

DateTime value;
if (!DateTime.TryParse(startDateTextBox.Text, out value))
{
    startDateTextox.Text = DateTime.Today.ToShortDateString();
}

Reasons for preferring this approach:

• Clearer code (it says what it wants to do)
• Better performance than catching and swallowing exceptions
• This doesn't catch exceptions inappropriately - e.g. OutOfMemoryException, ThreadInterruptedException. (Your current code could be fixed to avoid this by just catching the relevant exception, but using TryParse would still be better.)

All the Answers are Quite great but if you want to use a single function ,this may work. It will work with other date format but wont work with this date eg:05/06/202 it will consider it as valid date but it isnt.

private bool validateTime(string dateInString)
{
    DateTime temp;
    if (DateTime.TryParse(dateInString, out temp))
    {
       return true;
    }
    return false;
}

I would use the DateTime.TryParse() method: http://msdn.microsoft.com/en-us/library/system.datetime.tryparse.aspx

What about using TryParse?

A problem with using DateTime.TryParse is that it doesn't support the very common data-entry use case of dates entered without separators, e.g. 011508.

Here's an example of how to support this. (This is from a framework I'm building, so its signature is a little weird, but the core logic should be usable):

    private static readonly Regex ShortDate = new Regex(@"^\d{6}$");
    private static readonly Regex LongDate = new Regex(@"^\d{8}$");

    public object Parse(object value, out string message)
    {
        msg = null;
        string s = value.ToString().Trim();
        if (s.Trim() == "")
        {
            return null;
        }
        else
        {
            if (ShortDate.Match(s).Success)
            {
                s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 2);
            }
            if (LongDate.Match(s).Success)
            {
                s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 4);
            }
            DateTime d = DateTime.MinValue;
            if (DateTime.TryParse(s, out d))
            {
                return d;
            }
            else
            {
                message = String.Format("\"{0}\" is not a valid date.", s);
                return null;
            }
        }

    }

One liner:

if (DateTime.TryParse(value, out _)) {//dostuff}

You can also define the DateTime format for a specific CultureInfo

public static bool IsDateTime(string tempDate)
{
    DateTime fromDateValue;
    var formats = new[] { "MM/dd/yyyy", "dd/MM/yyyy h:mm:ss", "MM/dd/yyyy hh:mm tt", "yyyy'-'MM'-'dd'T'HH':'mm':'ss" };
    return DateTime.TryParseExact(tempDate, formats, System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out fromDateValue);
}

public static bool ValidateTime(string dateString)
{
    return DateTime.TryParse(dateString, out _);
}

protected static bool CheckDate(DateTime date)
{
    if(new DateTime() == date)      
        return false;       
    else        
        return true;        
}